Document support

[jayvdb]

Currently there is no handling for complete openapi documents.

Is this an appropriate direction to go in?

I've done some preliminary work, and will post a PR for consideration/ starting the ball rolling.

[pglass]

Overall, I'm generally not in favor, though not entirely against.

• It adds complexity which does not have to exist here. Full document processing can be done externally (right?). I've already punted on support for $ref fields, for example, which also must be handled externally.
• OpenAPI 3.1 will fully support JSON Schema, from what I understand, so this library will eventually become obsolete (emphasis on "eventually").
  • Here is an explanatory post on this by Phil Sturgeon.
  • However, OpenAPI 3.1 is still in RC and the tooling support for JSON Schema 2019-09 isn't yet there in Python, so it will be some time before this is a viable alternative.