<!-- This template is a great use for issues that are feature::additions or technical tasks for larger issues.--> ### Proposal We have long time open issues such as not being able to properly set up pages https://gitlab.com/gitlab-org/gitlab/-/issues/20184 if a username has a period. As a short term solution, I propose adding a warning if a user enters a period in the username when: 1. registering 1. changing their username While I'm not a fan of creating this as a "workaround" for another bug, changing a username can have a lot of side effects and may not be a feasible workaround, and the existing bug issue is a long standing one.