Add username check to doctor (#20140)
Add username check to doctor (#20140)

* Add username check to doctor

- Add a new breaking change detector to Gitea's doctor, which checks if
all users still have a valid username according to Gitea. Given from
time-to-time we need to make changes, either due to new routes or due to
security, it's for a instance's admin to check if all users still have a
valid username.

* Fix extra argument

* Apply suggestions from code review

Co-authored-by: Jimmy Praet <5f550c9a8c83bf5fa269f67259c7d3f6a3e8d5bc@telenet.be>

* Apply suggestions from code review

Co-authored-by: delvh <de75dc486f30b28015fd919fc5449eba02c6f8c6@web.de>

Co-authored-by: Jimmy Praet <5f550c9a8c83bf5fa269f67259c7d3f6a3e8d5bc@telenet.be>
Co-authored-by: John Olheiser <2efb384cc32e2c1c40c2368e43e7c46e52df9a2c@gmail.com>
Co-authored-by: techknowlogick <ff3785bfdd6690916cd886199c6b899e5f93e2e2@mdranta.net>
Co-authored-by: delvh <de75dc486f30b28015fd919fc5449eba02c6f8c6@web.de>
go-gitea/gitea,go-gitea/gitea,go-gitea/gitea