I'm working on a database design for a credit card processing web application. We are using single sign-on to authenticate users, so the username and password will not be stored in the database schema. What I'm trying to determine right now is when a user logs in if they are a first-time user or if they are a registered user. I have a contact table and I was thinking I could just add a new column to the contact table "registeredUser" that is a bit datatype. But, I'm wondering if this is limiting and if there was a better design choice. Please see the attached database diagram.
Thanks for any help from any database experts out there.