Add user: add the ability to use slashes in userName to allow to create users with domains like "DOMAIN\user1"

When single sign on is used the users are logined with "DOMAIN\user1" and, thus, FishEye is expected to provide such a possibility. When auto add-on is switched on the users with domains are added to the system properly but this auto add-on should be switched off in our case. It seems that this kind of validation(disallow slashes in the userName) is not principal, thus it would be useful if you provide the ability to use slashes in the usernames. Thanks.