This commit resolves a bug where users are not auto approved based on
`SiteSetting.auto_approve_email_domains` when
`SiteSetting.must_approve_users` has been enabled.
This commit introduces a new site setting: `use_name_for_username_suggestions` (default true)
Admins can disable it if they want to stop using Name values when generating usernames for users. This can be useful if you want to keep real names private-by-default or, when used in conjunction with the `use_email_for_username_and_name_suggestions` setting, you would prefer to use email-based username suggestions.
Alan Guo Xiang Tan
David Taylor
Andrei Prigorshnev