Multiple identical classes are generated for a component schema with allOf inheritance

When using inheritance using `allOf`, Kiota generates multiple identical classes for the same component schema. As a result, the types are incompatible when trying to consume the C# code generated by Kiota.

I've tried to create a minimal repro, but the OAS is still quite large. The full file is provided below. At a high level, the structure contains the following _base_ component schema:

```json
"dataInResponse": {
  "required": [
    "id",
    "type"
  ],
  "type": "object",
  "properties": {
    "type": {
      "minLength": 1,
      "type": "string"
    },
    "id": {
      "minLength": 1,
      "type": "string"
    }
  },
  "additionalProperties": false,
  "discriminator": {
    "propertyName": "type",
    "mapping": {
      "tags": "#/components/schemas/tagDataInResponse",
      "todoItems": "#/components/schemas/todoItemDataInResponse"
    }
  },
  "x-abstract": true
}
```

with _derived_ schemas `tagDataInResponse` and `todoItemDataInResponse`, ie:

```json
"todoItemDataInResponse": {
  "allOf": [
    {
      "$ref": "#/components/schemas/dataInResponse"
    },
    {
      "type": "object",
      "properties": {
        "attributes": {
          "allOf": [
            {
              "$ref": "#/components/schemas/todoItemAttributesInResponse"
            }
          ]
        },
        "relationships": {
          "allOf": [
            {
              "$ref": "#/components/schemas/todoItemRelationshipsInResponse"
            }
          ]
        }
      },
      "additionalProperties": false
    }
  ],
  "additionalProperties": false
}
```

These schemas are used from two GET endpoints, one returning a collection and the other a singular item. The response schema in both cases contains a `data` property (derived schema reference, or an array of that) and an `included` property (array of base schema reference).

The first endpoint (`paths./api/todoItems.get`) uses the following response schema:

```json
"todoItemCollectionResponseDocument": {
  "required": [
    "data"
  ],
  "type": "object",
  "properties": {
    "data": {
      "type": "array",
      "items": {
        "$ref": "#/components/schemas/todoItemDataInResponse"
      }
    },
    "included": {
      "type": "array",
      "items": {
        "$ref": "#/components/schemas/dataInResponse"
      }
    }
  },
  "additionalProperties": false
}
```

And the second endpoint (`paths./api/todoItems/{id}.get`) uses the following schema:

```json
"todoItemPrimaryResponseDocument": {
  "required": [
    "data"
  ],
  "type": "object",
  "properties": {
    "data": {
      "allOf": [
        {
          "$ref": "#/components/schemas/todoItemDataInResponse"
        }
      ]
    },
    "included": {
      "type": "array",
      "items": {
        "$ref": "#/components/schemas/dataInResponse"
      }
    }
  },
  "additionalProperties": false
}
```

I would have expected Kiota to generate the base class `DataInResponse`, with the two derived classes `TodoItemDataInResponse` and `TagDataInResponse`. What happens is that Kiota _also_ generates the derived class `TodoItems`, whose content is identical to `TodoItemDataInResponse`. The unexpected `TodoItems` class is only used by the singular endpoint.

As a result, it's not possible to define a method that takes a parameter of type `TodoItemDataInResponse` and is called with the response from _both_ endpoints. I would have expected to be able to write:
```c#
TodoItemPrimaryResponseDocument? getSingleResponse = await client.Api.TodoItems["1"].GetAsync();
PrintTodoItem(getSingleResponse!.Data!, getSingleResponse.Included);

TodoItemCollectionResponseDocument? getMultiResponse = await client.Api.TodoItems.GetAsync();
foreach (TodoItemDataInResponse todoItem in getMultiResponse!.Data!)
{
    PrintTodoItem(todoItem, getMultiResponse.Included);
}

static void PrintTodoItem(TodoItemDataInResponse todoItem, ICollection<DataInResponse>? included)
{
    // ...
}
```

Instead, the code for method `PrintTodoItem` needs to be duplicated, because the types are incompatible:
```c#
TodoItemPrimaryResponseDocument? getSingleResponse = await client.Api.TodoItems["1"].GetAsync();
PrintTodoItem1(getSingleResponse!.Data!, getSingleResponse.Included);

TodoItemCollectionResponseDocument? getMultiResponse = await client.Api.TodoItems.GetAsync();
foreach (TodoItemDataInResponse todoItem in getMultiResponse!.Data!)
{
    PrintTodoItem2(todoItem, getMultiResponse.Included);
}

static void PrintTodoItem1(TodoItems todoItem, ICollection<DataInResponse>? included)
{
    // ...
}

static void PrintTodoItem2(TodoItemDataInResponse todoItem, ICollection<DataInResponse>? included)
{
    // ...
}
```

Additionally, because there are duplicate types, it's unclear for consumers of the API what to upcast/type-check for when looping over the entries in `included`.

When using NSwag to generate the client, types appear as expected, which makes me believe the OAS is correct.

<details>
  <summary>Expand to view the full OAS file</summary>
  
```json
{
  "openapi": "3.0.1",
  "info": {
    "title": "JsonApiDotNetCoreExample",
    "version": "1.0"
  },
  "servers": [
    {
      "url": "https://localhost:44340"
    }
  ],
  "paths": {
    "/api/todoItems": {
      "get": {
        "tags": [
          "todoItems"
        ],
        "summary": "Retrieves a collection of todoItems.",
        "operationId": "getTodoItemCollection",
        "parameters": [
          {
            "name": "query",
            "in": "query",
            "description": "For syntax, see the documentation for the [`include`](https://www.jsonapi.net/usage/reading/including-relationships.html)/[`filter`](https://www.jsonapi.net/usage/reading/filtering.html)/[`sort`](https://www.jsonapi.net/usage/reading/sorting.html)/[`page`](https://www.jsonapi.net/usage/reading/pagination.html)/[`fields`](https://www.jsonapi.net/usage/reading/sparse-fieldset-selection.html) query string parameters.",
            "schema": {
              "type": "object",
              "additionalProperties": {
                "type": "string",
                "nullable": true
              },
              "example": ""
            }
          }
        ],
        "responses": {
          "200": {
            "description": "Successfully returns the found todoItems, or an empty array if none were found.",
            "content": {
              "application/vnd.api+json": {
                "schema": {
                  "$ref": "#/components/schemas/todoItemCollectionResponseDocument"
                }
              }
            }
          },
          "400": {
            "description": "The query string is invalid."
          }
        }
      }
    },
    "/api/todoItems/{id}": {
      "get": {
        "tags": [
          "todoItems"
        ],
        "summary": "Retrieves an individual todoItem by its identifier.",
        "operationId": "getTodoItem",
        "parameters": [
          {
            "name": "id",
            "in": "path",
            "description": "The identifier of the todoItem to retrieve.",
            "required": true,
            "schema": {
              "type": "string"
            }
          },
          {
            "name": "query",
            "in": "query",
            "description": "For syntax, see the documentation for the [`include`](https://www.jsonapi.net/usage/reading/including-relationships.html)/[`filter`](https://www.jsonapi.net/usage/reading/filtering.html)/[`sort`](https://www.jsonapi.net/usage/reading/sorting.html)/[`page`](https://www.jsonapi.net/usage/reading/pagination.html)/[`fields`](https://www.jsonapi.net/usage/reading/sparse-fieldset-selection.html) query string parameters.",
            "schema": {
              "type": "object",
              "additionalProperties": {
                "type": "string",
                "nullable": true
              },
              "example": ""
            }
          }
        ],
        "responses": {
          "200": {
            "description": "Successfully returns the found todoItem.",
            "content": {
              "application/vnd.api+json": {
                "schema": {
                  "$ref": "#/components/schemas/todoItemPrimaryResponseDocument"
                }
              }
            }
          },
          "400": {
            "description": "The query string is invalid."
          },
          "404": {
            "description": "The todoItem does not exist."
          }
        }
      }
    }
  },
  "components": {
    "schemas": {
      "dataInResponse": {
        "required": [
          "id",
          "type"
        ],
        "type": "object",
        "properties": {
          "type": {
            "minLength": 1,
            "type": "string"
          },
          "id": {
            "minLength": 1,
            "type": "string"
          }
        },
        "additionalProperties": false,
        "discriminator": {
          "propertyName": "type",
          "mapping": {
            "tags": "#/components/schemas/tagDataInResponse",
            "todoItems": "#/components/schemas/todoItemDataInResponse"
          }
        },
        "x-abstract": true
      },
      "tagAttributesInResponse": {
        "type": "object",
        "properties": {
          "name": {
            "minLength": 1,
            "type": "string"
          }
        },
        "additionalProperties": false
      },
      "tagDataInResponse": {
        "allOf": [
          {
            "$ref": "#/components/schemas/dataInResponse"
          },
          {
            "type": "object",
            "properties": {
              "attributes": {
                "allOf": [
                  {
                    "$ref": "#/components/schemas/tagAttributesInResponse"
                  }
                ]
              },
              "relationships": {
                "allOf": [
                  {
                    "$ref": "#/components/schemas/tagRelationshipsInResponse"
                  }
                ]
              }
            },
            "additionalProperties": false
          }
        ],
        "additionalProperties": false
      },
      "tagIdentifier": {
        "required": [
          "id",
          "type"
        ],
        "type": "object",
        "properties": {
          "type": {
            "$ref": "#/components/schemas/tagResourceType"
          },
          "id": {
            "minLength": 1,
            "type": "string"
          }
        },
        "additionalProperties": false
      },
      "tagRelationshipsInResponse": {
        "type": "object",
        "properties": {
          "todoItems": {
            "allOf": [
              {
                "$ref": "#/components/schemas/toManyTodoItemInResponse"
              }
            ]
          }
        },
        "additionalProperties": false
      },
      "tagResourceType": {
        "enum": [
          "tags"
        ],
        "type": "string",
        "additionalProperties": false
      },
      "toManyTagInResponse": {
        "type": "object",
        "properties": {
          "data": {
            "type": "array",
            "items": {
              "$ref": "#/components/schemas/tagIdentifier"
            }
          }
        },
        "additionalProperties": false
      },
      "toManyTodoItemInResponse": {
        "type": "object",
        "properties": {
          "data": {
            "type": "array",
            "items": {
              "$ref": "#/components/schemas/todoItemIdentifier"
            }
          }
        },
        "additionalProperties": false
      },
      "todoItemAttributesInResponse": {
        "type": "object",
        "properties": {
          "description": {
            "type": "string"
          }
        },
        "additionalProperties": false
      },
      "todoItemCollectionResponseDocument": {
        "required": [
          "data"
        ],
        "type": "object",
        "properties": {
          "data": {
            "type": "array",
            "items": {
              "$ref": "#/components/schemas/todoItemDataInResponse"
            }
          },
          "included": {
            "type": "array",
            "items": {
              "$ref": "#/components/schemas/dataInResponse"
            }
          }
        },
        "additionalProperties": false
      },
      "todoItemDataInResponse": {
        "allOf": [
          {
            "$ref": "#/components/schemas/dataInResponse"
          },
          {
            "type": "object",
            "properties": {
              "attributes": {
                "allOf": [
                  {
                    "$ref": "#/components/schemas/todoItemAttributesInResponse"
                  }
                ]
              },
              "relationships": {
                "allOf": [
                  {
                    "$ref": "#/components/schemas/todoItemRelationshipsInResponse"
                  }
                ]
              }
            },
            "additionalProperties": false
          }
        ],
        "additionalProperties": false
      },
      "todoItemIdentifier": {
        "required": [
          "id",
          "type"
        ],
        "type": "object",
        "properties": {
          "type": {
            "$ref": "#/components/schemas/todoItemResourceType"
          },
          "id": {
            "minLength": 1,
            "type": "string"
          }
        },
        "additionalProperties": false
      },
      "todoItemPrimaryResponseDocument": {
        "required": [
          "data"
        ],
        "type": "object",
        "properties": {
          "data": {
            "allOf": [
              {
                "$ref": "#/components/schemas/todoItemDataInResponse"
              }
            ]
          },
          "included": {
            "type": "array",
            "items": {
              "$ref": "#/components/schemas/dataInResponse"
            }
          }
        },
        "additionalProperties": false
      },
      "todoItemRelationshipsInResponse": {
        "type": "object",
        "properties": {
          "tags": {
            "allOf": [
              {
                "$ref": "#/components/schemas/toManyTagInResponse"
              }
            ]
          }
        },
        "additionalProperties": false
      },
      "todoItemResourceType": {
        "enum": [
          "todoItems"
        ],
        "type": "string",
        "additionalProperties": false
      }
    }
  }
}
```
</details>

I'm using the next command to generate the client code:
```bash
dotnet kiota generate --language CSharp --class-name ApiClient --namespace-name GeneratedClient --output ./GeneratedClient --clean-output --clear-cache --openapi ..\JsonApiDotNetCoreExample\GeneratedSwagger\JsonApiDotNetCoreExample.json
```

Used versions:
- .NET 8 SDK v8.0.201 on Windows 11 23H2
- microsoft.openapi.kiota global tool v1.11.1 (latest available)
- Latest available NuGet package versions, as of today:
    ```
    <PackageReference Include="Microsoft.Kiota.Abstractions" Version="1.7.9" />
    <PackageReference Include="Microsoft.Kiota.Http.HttpClientLibrary" Version="1.3.6" />
    <PackageReference Include="Microsoft.Kiota.Serialization.Form" Version="1.1.3" />
    <PackageReference Include="Microsoft.Kiota.Serialization.Json" Version="1.1.5" />
    <PackageReference Include="Microsoft.Kiota.Serialization.Multipart" Version="1.1.2" />
    <PackageReference Include="Microsoft.Kiota.Serialization.Text" Version="1.1.2" />
    ```


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Multiple identical classes are generated for a component schema with allOf inheritance #4191

bkoelman
openedon Feb 18, 2024

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Multiple identical classes are generated for a component schema with allOf inheritance #4191

Description

bkoelmanopenedon Feb 18, 2024

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