oauth: fix password-based login when username is email address

closes #199
2 jobs for bugfix/oauth-password-with-email in 4 minutes and 50 seconds (queued for 1 minute and 13 seconds)
latest
Status Job ID Name Coverage
  Lint
passed #5029
lint

00:02:05

 
  Test
passed #5030
unit-testing

00:02:45