How do you manage the oauth user_id vs. the username ?

[dorongutman]

When a user registers, he probably uses a username (or email) and a password.
But it seems you don't keep that username in the oauth context (i.e. for logging a user in, verifying his user/pass) but the user_id (a numeric id), even though the default for https://github.com/bshaffer/oauth2-server-php is using the same username used for the login.
How do you do that ?

Thanks.