MM-45994 ensure database operations return their errors (#20857)

store/sqlstore/thread_store.go

@@ -730,12 +730,12 @@ func (s *SqlThreadStore) DeleteMembershipForUser(userId string, postId string) e
 // - post creation (mentions handling)
 // - channel marked unread
 // - user explicitly following a thread
-func (s *SqlThreadStore) MaintainMembership(userId, postId string, opts store.ThreadMembershipOpts) (*model.ThreadMembership, error) {
+func (s *SqlThreadStore) MaintainMembership(userId, postId string, opts store.ThreadMembershipOpts) (_ *model.ThreadMembership, err error) {
 	trx, err := s.GetMasterX().Beginx()
 	if err != nil {
 		return nil, errors.Wrap(err, "begin_transaction")
 	}
-	defer finalizeTransactionX(trx)
+	defer finalizeTransactionX(trx, &err)
 
 	membership, err := s.getMembershipForUser(trx, userId, postId)
 	now := utils.MillisFromTime(time.Now())