Moves `Github.get_app()` called without `slug` parameter into `GithubIntegration`, because it needs an `AppAuth`,
and we collect all such endpoints there. Calling `Github.get_app()` without `slug` parameter is now deprecated.
Replaces `datetime.utcnow()` with `datetime.now(timezone.utc)`, as it is deprecated in Python 3.12.
This adds argument `auth` and deprecates `login_or_token`, `password`, `jwt`, and `app_auth` arguments of `github.Github`.
This adds argument `auth` and deprecates `integration_id`, `private_key` of `github.GithubIntegration`.
This deprecates the `create_jwt` method of `github.GithubIntegration`, replaced by `github.Auth.AppAuth.create_jwt`.
Enrico Minack