Allow maintainers to archive project

Description

GitLab's permissions currently aren't that fine-grained. We set permissions on group level, and only administrators get 'owner'; the group "below" that gets maintainer. We don't want that group to be able to delete projects or set the group visibility etc., but we would like them to be able to archive projects.

Proposal

We'd like to be able to have maintainers to be able to archive projects.