Use case: oauth2 access limited time tokens which should be updated on regular basis. Supplier allows us to move refresh logic outside client.
Use specified setter to set up supplier after gitlab api object creation.

Fix #769

Adding branches_to_be_notified to SlackService and deprecating notify_only_default_branch as per
https://docs.gitlab.com/ee/api/services.html#createedit-slack-service

based on docs https://docs.gitlab.com/ee/api/packages.html and inspired by GroupProjectsFilter

Added missing name attribute to Badges class. Also aligned indent of Badges class with rest of api.model package

https://docs.gitlab.com/ee/api/discussions.html#delete-a-merge-request-thread-note

Ensuring test SystemHooks are removed if tests fail, adding commentary/todo to address GitLab issue at future date

In GitLab 11.11, the Project Hook Key for wiki events was wiki_events.
We don't support GitLab 11.X. We only support GitLab 12.9.2+.
In new version of GitLab the correct key is wiki_page_events.