Fix GL_USERNAME including 'name' instead of 'username'
What does this MR do?
Fixes GL_USERNAME to use the username not the name. See https://gitlab.com/gitlab-org/gitlab-ce/issues/24945#note_44263757
Does this MR meet the acceptance criteria?
- Changelog entry added, if necessary
- Documentation created/updated
- API support added
- Tests added for this feature/bug
- Has been reviewed by UX
- Has been reviewed by Frontend
- Has been reviewed by Backend
- Has been reviewed by Database
- Conform by the merge request performance guides
- Conform by the style guides
- Squashed related commits together