[keycloak-user] Set up user attributes at account creation

Hi, Is there any possibility to automatically set up attributes (such as an unique integer Id) at account creation, with keycloak? I'm trying to set up a "rank" (1 for the first user, 2 for the second user, 3 for the third one) as an attribute and I'm having trouble to find out how I could « automate » this. Thanks, Rémy