I am going to be developing a site for a manufacturer that has a dealer network, each dealer has a dealer number they are associated with. My client wants me to have a dealer-only section on their site in which the user name is the dealer number. They want the dealer to be free to create their own account but be restricted to using their dealer number as username(matching a database on the back end, essentially a dealer number whitelist). Is this something that gravity forms can handle? if so, how?