Add Visualization API endpoint (#1565)

* Created visualization.proto

* Addressed most of PR feedback

* Fixed comments

* Addressed additional PR feedback

* Changed output from path to html

* Removed id parameter from visualization and changed inputPaths to inputPath

* Added support for command line arguments to be passed via the API

These are required for the new roc curve and will become import for passing any parameters form a user to the visualization.

* Fixed typo

backend/api/visualization.proto

@@ -0,0 +1,100 @@
+// Copyright 2019 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+syntax = "proto3";
+
+option go_package = "github.com/kubeflow/pipelines/backend/api/go_client";
+package api;
+
+import "google/api/annotations.proto";
+import "backend/api/error.proto";
+import "protoc-gen-swagger/options/annotations.proto";
+
+option (grpc.gateway.protoc_gen_swagger.options.openapiv2_swagger) = {
+  responses: {
+    key: "default";
+    value: {
+      schema: {
+        json_schema: {
+          ref: ".api.Status";
+        }
+      }
+    }
+  }
+  // Use bearer token for authorizing access to job service.
+  // Kubernetes client library(https://kubernetes.io/docs/reference/using-api/client-libraries/)
+  // uses bearer token as default for authorization. The section below
+  // ensures security definition object is generated in the swagger definition.
+  // For more details see https://github.com/OAI/OpenAPI-Specification/blob/3.0.0/versions/2.0.md#securityDefinitionsObject
+  security_definitions: {
+    security: {
+      key: "Bearer";
+      value: {
+        type: TYPE_API_KEY;
+        in: IN_HEADER;
+        name: "authorization";
+      }
+    }
+  }
+  security: {
+    security_requirement: {
+      key: "Bearer";
+      value: {};
+    }
+  }
+};
+
+service VisualizationService {
+  rpc CreateVisualization(CreateVisualizationRequest) returns (Visualization) {
+    option (google.api.http) = {
+      post: "/apis/v1beta1/visualizations"
+      body: "visualization"
+    };
+  }
+}
+
+// Create visualization by providing the type of visualization that is desired
+// and input data paths. Input dat paths are assumed to be unique and are used
+// for determining output path.
+message CreateVisualizationRequest {
+  Visualization visualization = 1;
+}
+
+message Visualization {
+  // Type of visualization to be generated.
+  // This is required when creating the pipeline through CreateVisualization
+  // API.
+  enum Type {
+    ROC_CURVE = 0;
+  };
+  Type type = 1;
+
+  // Path pattern of input data to be used during generation of visualizations.
+  // This is required when creating the pipeline through CreateVisualization
+  // API.
+  string inputPath = 2;
+
+  // Command line arguments to be used during generation of visualizations.
+  // This is required when creating the pipeline through CreateVisualization
+  // API.
+  repeated string arguments = 3;
+
+  // Output. Generated visualization html.
+  string html = 4;
+
+  // In case any error happens when generating visualizations, only
+  // visualization ID and the error message are returned. Client has the
+  // flexibility of choosing how to handle the error.
+  string error = 5;
+}