Request: Support List[pydantic.BaseModel] as response #56

Environment:

• Python version: 3.9.13
• Operating system: MacOS Monterey 12.4
• Flask version: 2.1.3
• flask-openapi3 version: 2.2.2

Request

Add support of List[] in responses.

Explanation

I'm trying to migrate an existing Flask API to Flask-OpenAPI, and I'm hitting an issue.

• Most of my endpoints return a JSON object, with the proper content type. This is compatible with the responses parameter in the @app.get decorator ✅
• Other endpoints return a simple string, with text content type. This is compatible with the extra_responses parameter ✅
• However, I do have a number of endpoints that return a JSON encoded list of objects, with content type JSON. This is not compatible with responses.

Since this API is used in production:

• I can't afford to wrap these lists in "dummy" object with a data key that would contain the list.
• I also don't really want to have to write a special dictionary to use in extra_responses. I tried using pydantic's schema_of function inside extra_responses, but that's not compatible because of the use of definitions.

Note that pydantic.schema_of(List[<child of pydantic.BaseModel>]) does work.