GitLab pages support for subgroups

Problem to Solve

GitLab now has support for subgroups, but Pages has not been updated to take account of this and Pages cannot be used at all with subgroups. This is an arbitrary limitation that keeps more users from being able to take advantage of using Pages.

Further details

Solution

Taking security and conflict possibilities into account, the best approach is: toplevel-group.gitlab.io/subgroup/project since this is the only variation we found that is guaranteed never to conflict.

We will add routing based on the above convention.

What does success look like, and how can we measure that?

Users are able to configure and deploy to GitLab pages for subgroup projects

Links / references

Documentation

We should describe the way this feature works on https://docs.gitlab.com/ee/administration/pages/. I'm not certain exactly which section it should go into, or if it should be its own section, but enabling pages on a subgroup and how the URL will work should be outlined.