Add support for plain text request body

[kairntech]

Is your feature request related to a problem? Please describe.
It should be possible to have endpoint with a full plain text request body like

  /dummy:
    post:
      requestBody:
        description: (to be documented)
        content:
          text/plain:
            schema:
              type: string
        required: true

Today it is completely ignored

Describe the solution you'd like
In openapi._add_body() we should have a additional line

        text_body, schemas = Endpoint.parse_request_text_body(
            body=data.requestBody, schemas=schemas, parent_name=endpoint.name, config=config
        )

And

    @staticmethod
    def parse_request_text_body(
        *, body: oai.RequestBody, schemas: Schemas, parent_name: str, config: Config
    ) -> Tuple[Union[Property, PropertyError, None], Schemas]:
        """Return text_body"""
        body_content = body.content
        text_body = body_content.get("text/plain")
        if text_body is not None and text_body.media_type_schema is not None:
            return property_from_data(
                name="text_body",
                required=True,
                data=text_body.media_type_schema,
                schemas=schemas,
                parent_name=parent_name,
                config=config,
            )
        return None, schemas

Describe alternatives you've considered

Additional context

[kairntech]

I can probably provide a PR

[rubenfiszel]

I am facing the same issue for response. text/plain does not seems to be supported

[dbanty]

This finally works with 0.16.0

[dbanty]

Clearly I did a bad job of searching for related discussions 🤦 . 0.16.0 added support for plain text responses, not requests.

[webbnh]

Thanks for the confirmation. (Sorry to bring the bad news....)

[webbnh]

It looks like replacing text/plain with application/octet-stream will work around the problem, at least for the moment.

[willr3]

We are also running into an issue generating a python client that consumes text/plain:

      requestBody:
        content:
          text/plain:
            schema:
              type: string

#> openapi-python-client --version
openapi-python-client version: 0.17.2

#> openapi-python-client generate --path ...
...
Unsupported content type text/plain

I am looking at changing the content type but are there plans to support the text/plain content type?

[marshalc]

Finding this whilst trying 0.22.0... turns out a large chunk of the API I'm trying to parse is either "Unsupported content type text/plain" or "Unsupported content type application/xml". If it helps, I've attached the file I'm working with - it comes from the NextGen Mirth Integration Engine

openapi.json