MM-41349: CRT, fix LastUpdated semantics (#19523)

* deadcode: remove UpdateChannelLastViewedAt

* deadcode: remove ThreadStore.(Save(Multiple)|Update|Delete)

* deadcode: followThead in App.MarkChannelAsUnreadFromPost

* document ThreadMembership, Thread structs

* maintain LastUpdated consistently

Whenever we touch a `ThreadMembership` record, we should be setting `LastUpdated` to the current timestamp. The mobile client relies on this to detect changes to these records.

* simplify: never updateThreads from `App.MarkChannelAsUnreadFromPost`

Change all invocations of `ChannelStore.UpdateLastViewedAtPost` from `App.MarkChannelAsUnreadFromPost` to pass `updateThreads` as `false`. When `ChannelStore.UpdateLastViewedAtPost` was invoked with `updateThreads` as `true`, it would in turn call `ThreadStore.UpdateUnreadsByChannel` but pass `updateViewedTimestamp` as `false`. This effectively updated the `LastUpdated` field of the corresponding thread memberships but never touched any of the actual data (such as `LastViewed`).

The overall CRT feature continued to work, because `App.MarkChannelAsUnreadFromPost` directly updates the relevant thread memberships via `ThreadStore.MaintainMembership`.

* deadcode: updateThreads in ChannelStore.UpdateLastViewedAtPost

* simplify: never updateThreads from App.SendNotifications

Change all invocations of `ChannelStore.IncrementMentionCount` from
`App.SendNotifications` to pass `updateThreads` as `false`. When `ChannelStore.IncrementMentionCount` was invoked with `updateThreads` as `true`, it would in turn call `ThreadStore.UpdateUnreadsByChannel` but pass `updateViewedTimestamp` as `false`. This effectively updated the `LastUpdated` field of the corresponding thread memberships but never touched any of the actual data (such as `UnreadMentions`).

The overall CRT feature continued to work, because `App.SendNotifications` directly updates the relevant thread memberships mention counts via `ThreadStore.MaintainMembership`.

* deadcode: updateThreads in ChannelStore.IncrementMentionCount

* fix & rename ThreadStore.UpdateUnreadsByChannel

Rename `ThreadStore.UpdateUnreadsByChannel` to `ThreadStore.UpdateLastViewedByThreadIds`, making it unconditionally set the `LastViewed` for the given threads (as well as `LastUpdated`).

All previous invocations of this method that passed `updateViewedTimestamp` have been previously removed.

* unrelated gofmt -w -s changes to satisfy linter

* always set LastUpdated to model.GetMillis()

* deadcode: ThreadStore.SaveMembership

* fix TestMarkUnreadWithThreads

* GetMasterX

store/retrylayer/retrylayer.go

@@ -1975,11 +1975,11 @@ func (s *RetryLayerChannelStore) GroupSyncedChannelCount() (int64, error) {
 
 }
 
-func (s *RetryLayerChannelStore) IncrementMentionCount(channelID string, userID string, updateThreads bool, isRoot bool) error {
+func (s *RetryLayerChannelStore) IncrementMentionCount(channelID string, userID string, isRoot bool) error {
 
 	tries := 0
 	for {
-		err := s.ChannelStore.IncrementMentionCount(channelID, userID, updateThreads, isRoot)
+		err := s.ChannelStore.IncrementMentionCount(channelID, userID, isRoot)
 		if err == nil {
 			return nil
 		}
@@ -2548,11 +2548,11 @@ func (s *RetryLayerChannelStore) UpdateLastViewedAt(channelIds []string, userID
 
 }
 
-func (s *RetryLayerChannelStore) UpdateLastViewedAtPost(unreadPost *model.Post, userID string, mentionCount int, mentionCountRoot int, updateThreads bool, setUnreadCountRoot bool) (*model.ChannelUnreadAt, error) {
+func (s *RetryLayerChannelStore) UpdateLastViewedAtPost(unreadPost *model.Post, userID string, mentionCount int, mentionCountRoot int, setUnreadCountRoot bool) (*model.ChannelUnreadAt, error) {
 
 	tries := 0
 	for {
-		result, err := s.ChannelStore.UpdateLastViewedAtPost(unreadPost, userID, mentionCount, mentionCountRoot, updateThreads, setUnreadCountRoot)
+		result, err := s.ChannelStore.UpdateLastViewedAtPost(unreadPost, userID, mentionCount, mentionCountRoot, setUnreadCountRoot)
 		if err == nil {
 			return result, nil
 		}
@@ -10540,27 +10540,6 @@ func (s *RetryLayerThreadStore) CollectThreadsWithNewerReplies(userId string, ch
 
 }
 
-func (s *RetryLayerThreadStore) Delete(postID string) error {
-
-	tries := 0
-	for {
-		err := s.ThreadStore.Delete(postID)
-		if err == nil {
-			return nil
-		}
-		if !isRepeatableError(err) {
-			return err
-		}
-		tries++
-		if tries >= 3 {
-			err = errors.Wrap(err, "giving up after 3 consecutive repeatable transaction failures")
-			return err
-		}
-		timepkg.Sleep(100 * timepkg.Millisecond)
-	}
-
-}
-
 func (s *RetryLayerThreadStore) DeleteMembershipForUser(userId string, postID string) error {
 
 	tries := 0
@@ -10918,84 +10897,21 @@ func (s *RetryLayerThreadStore) PermanentDeleteBatchThreadMembershipsForRetentio
 
 }
 
-func (s *RetryLayerThreadStore) Save(thread *model.Thread) (*model.Thread, error) {
+func (s *RetryLayerThreadStore) UpdateLastViewedByThreadIds(userId string, threadIds []string, timestamp int64) error {
 
 	tries := 0
 	for {
-		result, err := s.ThreadStore.Save(thread)
+		err := s.ThreadStore.UpdateLastViewedByThreadIds(userId, threadIds, timestamp)
 		if err == nil {
-			return result, nil
+			return nil
 		}
 		if !isRepeatableError(err) {
-			return result, err
+			return err
 		}
 		tries++
 		if tries >= 3 {
 			err = errors.Wrap(err, "giving up after 3 consecutive repeatable transaction failures")
-			return result, err
-		}
-		timepkg.Sleep(100 * timepkg.Millisecond)
-	}
-
-}
-
-func (s *RetryLayerThreadStore) SaveMembership(membership *model.ThreadMembership) (*model.ThreadMembership, error) {
-
-	tries := 0
-	for {
-		result, err := s.ThreadStore.SaveMembership(membership)
-		if err == nil {
-			return result, nil
-		}
-		if !isRepeatableError(err) {
-			return result, err
-		}
-		tries++
-		if tries >= 3 {
-			err = errors.Wrap(err, "giving up after 3 consecutive repeatable transaction failures")
-			return result, err
-		}
-		timepkg.Sleep(100 * timepkg.Millisecond)
-	}
-
-}
-
-func (s *RetryLayerThreadStore) SaveMultiple(thread []*model.Thread) ([]*model.Thread, int, error) {
-
-	tries := 0
-	for {
-		result, resultVar1, err := s.ThreadStore.SaveMultiple(thread)
-		if err == nil {
-			return result, resultVar1, nil
-		}
-		if !isRepeatableError(err) {
-			return result, resultVar1, err
-		}
-		tries++
-		if tries >= 3 {
-			err = errors.Wrap(err, "giving up after 3 consecutive repeatable transaction failures")
-			return result, resultVar1, err
-		}
-		timepkg.Sleep(100 * timepkg.Millisecond)
-	}
-
-}
-
-func (s *RetryLayerThreadStore) Update(thread *model.Thread) (*model.Thread, error) {
-
-	tries := 0
-	for {
-		result, err := s.ThreadStore.Update(thread)
-		if err == nil {
-			return result, nil
-		}
-		if !isRepeatableError(err) {
-			return result, err
-		}
-		tries++
-		if tries >= 3 {
-			err = errors.Wrap(err, "giving up after 3 consecutive repeatable transaction failures")
-			return result, err
+			return err
 		}
 		timepkg.Sleep(100 * timepkg.Millisecond)
 	}
@@ -11023,27 +10939,6 @@ func (s *RetryLayerThreadStore) UpdateMembership(membership *model.ThreadMembers
 
 }
 
-func (s *RetryLayerThreadStore) UpdateUnreadsByChannel(userId string, changedThreads []string, timestamp int64, updateViewedTimestamp bool) error {
-
-	tries := 0
-	for {
-		err := s.ThreadStore.UpdateUnreadsByChannel(userId, changedThreads, timestamp, updateViewedTimestamp)
-		if err == nil {
-			return nil
-		}
-		if !isRepeatableError(err) {
-			return err
-		}
-		tries++
-		if tries >= 3 {
-			err = errors.Wrap(err, "giving up after 3 consecutive repeatable transaction failures")
-			return err
-		}
-		timepkg.Sleep(100 * timepkg.Millisecond)
-	}
-
-}
-
 func (s *RetryLayerTokenStore) Cleanup(expiryTime int64) {
 
 	s.TokenStore.Cleanup(expiryTime)