Use internal-gitlab-server in Auth package

What does this MR do?

Closes #581 (closed)
Closes #559 (closed)

TODO

• I added the Changelog (e.g. Changelog: feature) trailer to the commits that need to be included in the changelog
• I added unit tests or they are not required
• I added acceptance tests or they are not required
• I added documentation (or it's not required)
• I followed code review guidelines
• I followed Go Style guidelines