WIP: Per Job status updates sent by GithubService

What

Notifies GitHub as jobs are updates, allowing a status check to be shown per job. Continues to send existing notification per pipeline.

Why

• When a user makes a pull request in GitHub they get a detailed information about builds in realtime
• Allows our CI to be used in conjunction with GitHub's "Required Status Checks" feature by having a context which users can mark as required. With pipeline updates we needed to include ref name, but this means the context is different on every branch or tag.

Screenshots

GitHub-status-check

Acceptance criteria

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Internationalization required/considered
• End-to-end tests pass (package-qa manual pipeline job)

Related

Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/5041