Consider handling of associated_external_type for all types

[bendbennett]

Within a specification defined by the schema within the terraform-plugin-codegen-spec repo, associated_external_type is property that can be optionally defined for

• nested_object within list_nested, map_nested, and set_nested attributes
• single_nested attributes
• nested_object within list_nested, and set_nested blocks
• single_nested blocks

The associated_external_type field is used during code generation to signal that methods which transform to and from Terraform Plugin Framework types to API SDK types for use with API calls be autogenerated.

For example, usage of associated_external_type in the following specification results in the generation of the To<...>()/From<...>() methods.

{
  "datasources": [
    {
      "name": "example",
      "schema": {
        "attributes": [
          {
            "name": "list_nested_attribute",
            "list_nested": {
              "nested_object": {
                "associated_external_type": {
                  "import": {
                    "path": "example.com/apisdk"
                  },
                  "type": "*apisdk.Type"
                },
                "attributes": [
                  {
                    "name": "int64_attribute",
                    "int64": {
                      "computed_optional_required": "optional"
                    }
                  }
                ]
              },
              "computed_optional_required": "optional"
            }
          }
        ]
      }
    }
  ],
  "provider": {
    "name": "example"
  }
}

func (v ListNestedAttributeValue) ToApisdkType(ctx context.Context) (*apisdk.Type, diag.Diagnostics) {
	var diags diag.Diagnostics

	if v.IsNull() {
		return nil, diags
	}

	if v.IsUnknown() {
		diags.Append(diag.NewErrorDiagnostic(
			"ListNestedAttributeValue Value Is Unknown",
			`"ListNestedAttributeValue" is unknown.`,
		))

		return nil, diags
	}

	return &apisdk.Type{
		Int64Attribute: v.Int64Attribute.ValueInt64Pointer(),
	}, diags
}

func (v ListNestedAttributeValue) FromApisdkType(ctx context.Context, apiObject *apisdk.Type) (ListNestedAttributeValue, diag.Diagnostics) {
	var diags diag.Diagnostics

	if apiObject == nil {
		return NewListNestedAttributeValueNull(), diags
	}

	return ListNestedAttributeValue{
		Int64Attribute: types.Int64PointerValue(apiObject.Int64Attribute),
		state:          attr.ValueStateKnown,
	}, diags
}

Proposal

Extension of the handling of associated_external_type for other types (e.g., bool attributes, list attributes) should be considered.