feat: exceptions for auth errors 400, 401, 403

[davidhuser]

related to #229

• introduce new exceptions including a factory to assign exceptions based on starlette.request type (http or websocket)
• updated the contributor guide
• fixed a minor mypy issue preventing pre-commit

[davidhuser]

failing linting tests in demo_project but these seem unrelated to this PR. How should we proceed?

[JonasKs]

I really like this, thanks!! I have some concerns about backwards compatibility, since I'd prefer not to major bump again 😁 Could we ensure that the old InvalidAuthHttp is a base? So anyone importing it, or catching it, will still catch all exceptions?

Something like this, I think would work?

class InvalidAuth(HTTPException):
    ...

class ForbiddenHttp(InvalidAuth, HTTPException):
    ...

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failing linting tests in demo_project but these seem unrelated to this PR. How should we proceed?

Ignore. I'll look into this another time. It won't block merge 😊