MM-34609 Mark-as-unread on a post in a thread should cause auto-follow (#17343)

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

store/retrylayer/retrylayer.go

@@ -9298,21 +9298,21 @@ func (s *RetryLayerThreadStore) GetThreadsForUser(userId string, teamID string,
 
 }
 
-func (s *RetryLayerThreadStore) MaintainMembership(userID string, postID string, following bool, incrementMentions bool, updateFollowing bool, updateViewedTimestamp bool) error {
+func (s *RetryLayerThreadStore) MaintainMembership(userID string, postID string, following bool, incrementMentions bool, updateFollowing bool, updateViewedTimestamp bool) (*model.ThreadMembership, error) {
 
 	tries := 0
 	for {
-		err := s.ThreadStore.MaintainMembership(userID, postID, following, incrementMentions, updateFollowing, updateViewedTimestamp)
+		result, err := s.ThreadStore.MaintainMembership(userID, postID, following, incrementMentions, updateFollowing, updateViewedTimestamp)
 		if err == nil {
-			return nil
+			return result, nil
 		}
 		if !isRepeatableError(err) {
-			return err
+			return result, err
 		}
 		tries++
 		if tries >= 3 {
 			err = errors.Wrap(err, "giving up after 3 consecutive repeatable transaction failures")
-			return err
+			return result, err
 		}
 	}