Return @dataclasses objects instead of primitives in request.openapi_validated

[zupo]

Instead of having strings, ints, etc in request.openapi_validated we could have dataclass objects that match the schema and provide type protection.

[zupo]

Similar idea: https://github.com/graphql-python/graphene/issues/729#issuecomment-393673570

[domenkozar]

https://github.com/p1c2u/openapi-core/issues/88

[zupo]

It seems pyramid-swagger can generate python models on the fly: https://pyramid-swagger.readthedocs.io/en/latest/quickstart.html#accessing-request-data