Fix gitlab pages on alternate port

What does this MR do?

If you are running GitLab pages on a custom port (anything other than 80/443) /var/opt/gitlab/gitlab-pages/gitlab-pages-config is currently generating an incorrect auth-redirect-uri (ignoring the port).

In my instance, the pages setup in /etc/gitlab/gitlab.rb includes pages_external_url "http://pages.domain.com:8443/" but the generated /var/opt/gitlab/gitlab-pages/gitlab-pages-config contains auth-redirect-uri=http://projects.pages.domain.com/auth

Fortunately I found that it is possible to override this by setting gitlab_pages['auth_redirect_uri'] in /etc/gitlab/gitlab.rb- but it seems like this should "just work" :)

Related issues

Checklist

See Definition of done.

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Required

• Merge Request Title, and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com
• Pipeline is green on dev.gitlab.org if the change is touching anything besides documentation or internal cookbooks
• trigger-package has a green pipeline running against latest commit

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• Documentation created/updated
• Tests added
• Integration tests added to GitLab QA
• Equivalent MR/issue for the GitLab Chart opened