Hello All,
Wanting to write Apex Code (Both Class and Trigger) to auto assign Users who are assign to Permission Set (Test) to a Community Chatter group. 
I Manage to assign to a community chatter group based on Profile but not Based on Permission set. Could you please help?

Below is my code based on Profile. 
trigger User_trigger on User (after insert, before insert, after update, before update) {

    if ( Trigger.isInsert ) {   

        if ( Trigger.isAfter ) {

            List<id> UserIds = new List<id>();

            for ( user u: Trigger.new ) {

                if ( u.Profile.UserLicense.Name <> 'Customer Community Plus' ) {

                    UserIds.add(u.id);

                }                

            }

            if ( UserIds.size() > 0 ) {

                asyncApex.addUserToGroup(UserIds); 

            }          

        }

    }

global class AsyncApex {

    @future

    public static void AddUserToGroup(List<ID> UserIds) {

        try {

            List<CollaborationGroupMember> cgm = new List<CollaborationGroupMember>();                     

            Id cgID = [ Select Id

                        FROM CollaborationGroup

                        WHERE Name = 'All Clients Groups' LIMIT 1 ].ID;

           for ( Id UserId : UserIds ) {

               cgm.add(new CollaborationGroupMember (CollaborationGroupId = cgID, MemberId = UserId));  

           }

           insert cgm;

        } catch (QueryException qe) {

            System.debug('QueryException in AsyncApex.AddUserToGroup is :' + qe); 

        } catch (Exception ex) {

            System.debug('Exception in AsyncApex.AddUserToGroup is :' + ex);

        }   

    }

}