Make GitLab pages support access control

What does this MR do?

Adds option to use GitLab access control in project pages #33422 (closed) and implement the necessary changes for pages config file generation.

This depends on the pages MR gitlab-pages!94 (merged).

The changes required for GitLab to automatically configure necessary pages client id, secret etc. are implemented in omnibus-gitlab!2583 (merged).

All feedback is appreciated!

Testing

At the moment this can be tested by creating the authentication id and secret manually and compiling GitLab pages from gitlab-pages branch.

CI

I haven't done any changes to gitlab-ee so the ee_compat_check job is failing at the moment.

Are there points in the code the reviewer needs to double check?

Not that I know of.

Why was this MR needed?

Closes #33422 (closed).

Screenshots (if relevant)

Does this MR meet the 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 Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered
• End-to-end tests pass (package-and-qa manual pipeline job)

What are the relevant issue numbers?

#33422 (closed)