Include current attribute path in validator diag message for `ExactlyOneOf`

[austinvalle]

Terraform CLI and Framework Versions

Terraform v1.3.8
on darwin_arm64

github.com/hashicorp/terraform-plugin-framework v1.1.1

Use Cases or Problem Statement

Given the following resource schema + config:

// example_widget Resource
resp.Schema = schema.Schema{
	// ... other configuration ...

	Attributes: map[string]schema.Attribute{
		// ... other attributes ...

		"existing_attribute": schema.StringAttribute{
			Optional:           true,
		},
		"new_attribute": schema.StringAttribute{
			Optional: true,
			Validators: []validator.String{
				stringvalidator.ExactlyOneOf(path.Expressions{
					path.MatchRoot("existing_attribute"),
				}...),
			},
		},
	},
}

resource "example_widget" "example" {
  existing_attribute = "there can"
  new_attribute      = "only be one"
}

Produces a validation error correctly, but does not include the path of the attribute that the validation is applied to new_attribute:

│ Error: Invalid Attribute Combination
│ 
│   with example_widget.example,
│   on main.tf line 11, in resource "example_widget" "example":
│   11:   new_attribute      = "only be one"
│ 
│ 2 attributes specified when one (and only one) of [existing_attribute] is required

Proposal

Add the path of the attribute that the validator is applied to, to the validation diag message, like:

│ Error: Invalid Attribute Combination
│ 
│   with example_widget.example,
│   on main.tf line 11, in resource "example_widget" "example":
│   11:   new_attribute      = "only be one"
│ 
│ 2 attributes specified when one (and only one) of [new_attribute, existing_attribute] is required

Additional Information

N/A

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