Currently our `gitlab-config.git` repo is only accessible to sysadmins. IMO at least `committers-team` should be allowed to clone, and propose MRs against, that repo. This would address a number of problems: * RMs could open MRs for group milestones changes they have to do (see tails@b170e12805484432786e528b0d36580cc4f67c8f). * Committers could propose new group labels: in the last few days, 2 tails/tails project labels were created (because committers are allowed to do that, but they can't edit group labels) while these should really have been group labels. * When a team onboards a new member or offboards a previous member, perhaps they could send a MR for the corresponding GitLab group membership change. * Committers could propose new projects under the `tails/` namespace, ensuring our common project settings & permission model are applied. I propose we: - [x] migrate `gitlab-config.git` to GitLab - [x] allow committers to clone that repo and push to non-protected branches - [x] document how to propose changes to our GitLab config I volunteer to do all this once we agree on something.