BaseModel Config support openapi_extra

[luolingchun]

class BookBody(BaseModel):
    age: Optional[int] = Field(..., ge=2, le=4, description='Age')
    author: str = Field(None, min_length=2, max_length=4, description='Author')

    class Config:
        openapi_extra = {
            "description": "This is post RequestBody",
            "example": {
                "age": 12,
                "author": "author"
            },
            "examples": {
                "example1": {
                    "summary": "example summary1",
                    "description": "example description1",
                    "value": {
                        "age": 24,
                        "author": "author1"
                    }
                },
                "example2": {
                    "summary": "example summary2",
                    "description": "example description2",
                    "value": {
                        "age": 48,
                        "author": "author2"
                    }
                }
            }
        }

DeprecationWarning:
extra_form , extra_body and extra_responses will be deprecated in v3.x ???