[Question]: RequestBody & Multiple Content-Types

Support for multiple content-types in RequestBody

In the documentation can be find a OpenApi example with multiple content-types in requestBody. But in the code is a index with 0 fix implement.

When is it planned to handling multiple content-types in requestBody ?

paths:
  /services/T00000000/B00000000/XXXXXXXXXXXXXXXXXXXXXXXX:
    post:
      summary: Post a message to Slack
      requestBody:
        content:
        
          application/json:
            schema:
              $ref: '#/components/schemas/Message'
          application/x-www-form-urlencoded:
            schema:
              type: object
              properties:
                payload:     # <--- form field that contains the JSON message
                  $ref: '#/components/schemas/Message'
            encoding:
              payload:
                contentType: application/json

https://github.com/OpenAPITools/openapi-generator/blob/master/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java

  protected String getContentType(RequestBody requestBody) {
        if (requestBody == null || requestBody.getContent() == null || requestBody.getContent().isEmpty()) {
            return null;
        }
        return new ArrayList<>(requestBody.getContent().keySet()).get(0);
    }

Start in modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java, especially getContentType(RequestBody), and compare it with the multiple-content-type RequestBody example in the issue. Determine the expected generated behavior for each content type and identify the affected generators before defining completion criteria and tests.