This change modernizes the base classes for hosting services, primarily

adding type annotations and correcting docstrings.
The authorize and check_repository methods have been made

keyword-only. These were already called by unpacking a dict, and in

practice many of the individual implementations had inconsistent

argument lists which would have made calling with positional arguments

fail. The only places where we were using positional args were in a few

unit tests, which have been updated. I've added

@deprecate_non_keyword_only_args, but given the existing

inconsistencies, we could probably do this change without a deprecation

phase at all.

Ran unit tests.