[keycloak-user] Different username for direct access grant?

Hi! We're integrating our Java application with Keycloak using JAAS. We're making use of org.keycloak.adapters.jaas.DirectAccessGrantsLoginModule For this application, we'd like the users to authenticate with a username that is different from the "username" property in the Keycloak UserModel. Instead, we'd like to use the Keycloak ID. I had thought that changing the "username" protocol mapping for the client that is used would do the trick. I changed the value for the "property" field from "username" to "id" - that does not have the desired effect, as users can still log in with their 'username' (instead of the UUID value that is the Keycloak ID. What is my mistake? Regards, Guus