[keycloak-user] Multiple 'user' data-source ?

Hi, My company is aiming at building its own OpenId Connect provider, for our internal apps. Thus we are looking for an open source framework. KeyCloak seems very good. Unfortunatly, we have a problem, and I did not find if KeyCloak can solve it: Our 'users' are store in an AD directory or in a database (postgree). To sum up: if the user is not in the AD, then we should look in the databse . Is this doable with Keylcloak?? Thanks.