Hi @MetaFight, Welcome to SavaPage and thank you for pointing out the Open Source Keycloak OAuth solution. Synchronizing both Keycloak and SavaPage with your OpenLDAP server is indeed a prerequisite for Keycloak OAuth to work. Indeed, savapage-ext-oauth is the right place to find out that the Keycloak OAuth client was missing.
Since it is quite easy to add OAuth providers, I just created KeycloakOAuthPlugin.java with the savapage-ext-oauth-keycloak.properties.template. They are ready to test in SavaPage Release Candidate 2020-10-04 or later (see this issue).
Can you please reply to this post about OAuth to share your test results? Of course, pull requests for the Java code are welcome as well. Good luck!