* 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
6757edc4e2