Use this class to find members within the Groups registry
Sample call
Set members = MemberFinder.findAll(grouperSession, gsaSource);
Sample call to find members by attribute def names
Set members = new MemberFinder().assignNameOfAttributeDefName(attributeDefName.getName())
.assignAttributeCheckReadOnAttributeDef(true).assignQueryOptions(QueryOptions.create("subjectId", true, null, null)).findMembers();