Support multi content type in request body and responses

[luolingchun]

Checklist:

• Run pytest tests and no failed.
• Run ruff check flask_openapi3 tests examples and no failed.
• Run mypy flask_openapi3 and no failed.
• Run mkdocs serve and no failed.

Many people have multi content-type needs:

• Add support for multiple custom JSON content types in the request body #100
• Unable to support response description with the same output schema and different response content-types #204
• Support multiple media types under the same status code #207
• Support request body and multiple media types under the same status code #208

[luolingchun]

@joaopedroft @raisachatterjee @iongion

I'm sorry to bother you, but I hope you can do some testing and give some advice.

I have already released a beta version 4.1.0rc1.

Update in 2025.2.8 4.2.0rc1.