### Summary "Username ending with MIME type format is not allowed" Can be problematic, especially for SSO/OAuth/SAML logins where the username is automatically defined This issue is reproducible on on-premises **and** Gitlab.com (ex: with Google Login), either from the login page and/or when attempting to create the user manually from the Admin area. -mov being a common family name suffix, it could cause a lot of issues in the future ### Steps to reproduce Try to login/create an user in Gitlab (on-premises/Gitlab.com) where the username ends with a MIME type format ### What is the current *bug* behavior? Username ending with MIME type format is not allowed ### What is the expected *correct* behavior? Username ending with MIME type format should be allowed to login and/or create account on Gitlab (on-premises/Gitlab.com) ### Relevant logs and/or screenshots  - - -  ### Possible fixes https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/models/user.rb#L2102 https://gitlab.com/gitlab-org/gitlab/-/blob/master/spec/models/user_spec.rb#L391 https://gitlab.com/gitlab-org/gitlab/-/blob/master/config/initializers/mime_types.rb#L14