Hi Nat, as Demian mentioned, we added a user/group callback interface that users can implement and hook to their identity management (LDAP, Database, etc). The interface is very simple:
package org.jbpm.task.service;
import java.util.List;
public interface UserGroupCallback {
boolean existsUser(String userId);
boolean existsGroup(String groupId);
List<String> getGroupsForUser(String userId);
}
(https://github.com/droolsjbpm/jbpm/blob/master/jbpm-human-task/src/main/java/org/jbpm/task/service/UserGroupCallback.java)
The task service then contacts this user/group callback service whenever necessary. Since this has been added fairly recently we are still working on creating examples and updating the docs. Should be done with that really soon.
Hope this helps.