Patch proposal for issue when ldap user log in for the first time

There is an issue described in https://stackoverflow.com/questions/24972686/ldap-with-gitlab-undefined-method-persisted I found a patch that allow an ldap user to log in for the first time. The bug occurs when gitlab whant to create the user instance in the database, because the username choosen by default is the email address (perhaps because of a custom ldap configuration : in my case le username/loggin is the "xmozillanickname" attribute). This patch force to use the gitlab ldap "uid" custom field configuration.