[keycloak-user] (no subject)

Hello, I am trying to set-up a user federation. My project involves an external database. Currently no user data has to be imported from the external database. Changes in keycloak need to be exported to the external database. We don't want to validate logins against the external database. Could someone explain to me how to validate a user login against the keycloak database? This would be while using the "validCredentials(RealmModel realm, UserModel user, List<UserCredentialModel> input)" method. Thanks in advance. Sincerely, Frank van Veen