Parse and validate API parameters from OpenAPI

[obiyankenobi]

From this comment. @msbrogli suggested:

"Instead of manually validating each input, isn't it easier to get the basic validation rules from the OpenAPI Specification of each API?

I'd say we would be able to validate 99% of the input errors using it, and it would also return the parsed object. Maybe we should have a ParsedQuery object with the types so mypy can check the types as well."