login name can be different from user id even when use_email_as_login is False

I have users that have UUID-based user ids and login names that are not based on the email address.

I'm trying to deal with this by looking up what the user entered as a login name first, regardless of the use_email_as_login setting, and then assume it's a userid if nothing was found.

@mauritsvanrees, does this make sense to you?