Keycloak roles should sync immediately to authz

[leafty]

Currently, if the renku_admin role is removed from a user in Keycloak, it may take up to 3 hours for that change to be synced into authz. This may give unwanted permissions on groups, projects, etc.

[leafty]

Seems that resolving #998 would fix this: if we sync using Keycloak events continuously, then the role change should be reflected quickly.