RFC: Make OAuth*Problem extend ProblemException instead of werkzeug

[cognifloyd]

Description

I wonder if these should extend ProblemException instead of the werkzeug exceptions.

• connexion.exceptions.OAuthProblem(werkzeug.exceptions.Unauthorized)
• connexion.exceptions.OAuthResponseProblem(OAuthProblem)
• connexion.exceptions.OAuthScopeProblem(werkzeug.exceptions.Forbidden)

I'm not sure the logic behind not using ProblemException for these. I wonder if it has something to do with making it more secure or to get better handling in Flask.
Ultimately it feels out of place when you consider adding aiohttp (and other frameworks #828 #440) support.

This is related to #955, and could be included in it, but seems slightly orthogonal to that effort.

Expected behaviour

Don't extend a framework specific exception inside Zalando core.

Actual behaviour

Aiohttp ends up using the werkzeug exceptions.

Steps to reproduce

Read the code.

[cognifloyd]

The docs are incorrect. They say that OAuthProblem extends both Unauthorized and ProblemException which would probably be good enough to allow better framework interchangeability without using werkzeug directly in, for example, aiohttp.
https://connexion.readthedocs.io/en/latest/exceptions.html?highlight=ProblemException

https://github.com/zalando/connexion/blob/d8cd116154c957e0a9f0abb321189b29f2b6a10e/docs/exceptions.rst#L9-L10
https://github.com/zalando/connexion/blob/d8cd116154c957e0a9f0abb321189b29f2b6a10e/docs/exceptions.rst#L18-L28
https://github.com/zalando/connexion/blob/fda2b18b38f4f3dc26338195240ffb7a77f5c6db/connexion/exceptions.py#L81-L96

[cognifloyd]

The code changed away from what is listed in the doc in bce907f

This section of the doc hasn't changed since added in 7a9329f