[MM-41185]: new API to mark thread as unread (#19951)

* [MM-41185]: new API to mark thread as unread

Until now we mark a thread as read/unread by sending a timestamp to the
server. This created some issues when marking a thread as unread from a
post. We needed to send the post.create_at - 1 as a timestamp but we
didn't do so consistently.

This commit adds a new API to set a thread as unread by post id.
Making all clients agnostic of the timestamp, and thus solving consistency issues.

Endpoint: /api/v4/users/{user_id}/teams/{team_id}/threads/{thread_id}/set_unread/{post_id}

* Updates client.go adding SetThreadUnreadByPostId

* Guards endpoint behind read channel permission

* Returns status 400 if post_id not belong in thread

* Root post as post_id should be permitted

api4/user_test.go

@@ -5998,7 +5998,7 @@ func TestThreadSocketEvents(t *testing.T) {
 		require.Truef(t, caught, "User should have received %s event", model.WebsocketEventThreadReadChanged)
 	})
 
-	_, resp, err = th.Client.UpdateThreadReadForUser(th.BasicUser.Id, th.BasicTeam.Id, rpost.Id, rpost.CreateAt)
+	_, resp, err = th.Client.SetThreadUnreadByPostId(th.BasicUser.Id, th.BasicTeam.Id, rpost.Id, rpost.Id)
 	require.NoError(t, err)
 	CheckOKStatus(t, resp)
 
@@ -6012,7 +6012,7 @@ func TestThreadSocketEvents(t *testing.T) {
 						caught = true
 
 						data := ev.GetData()
-						require.EqualValues(t, rpost.CreateAt, data["timestamp"])
+						require.EqualValues(t, rpost.CreateAt-1, data["timestamp"])
 						require.EqualValues(t, float64(0), data["previous_unread_replies"])
 						require.EqualValues(t, float64(0), data["previous_unread_mentions"])
 						require.EqualValues(t, float64(1), data["unread_replies"])
@@ -6473,7 +6473,7 @@ func TestReadThreads(t *testing.T) {
 		require.Greater(t, uss2.Threads[0].LastViewedAt, uss.Threads[0].LastViewedAt)
 	})
 
-	t.Run("1 thread", func(t *testing.T) {
+	t.Run("1 thread by timestamp", func(t *testing.T) {
 		defer th.App.Srv().Store.Post().PermanentDeleteByUser(th.BasicUser.Id)
 		defer th.App.Srv().Store.Post().PermanentDeleteByUser(th.SystemAdminUser.Id)
 
@@ -6500,6 +6500,42 @@ func TestReadThreads(t *testing.T) {
 		uss3, _ := checkThreadListReplies(t, th, th.Client, th.BasicUser.Id, 1, 2, nil)
 		require.Equal(t, uss3.Threads[0].LastViewedAt, timestamp)
 	})
+
+	t.Run("1 thread by post id", func(t *testing.T) {
+		defer th.App.Srv().Store.Post().PermanentDeleteByUser(th.BasicUser.Id)
+		defer th.App.Srv().Store.Post().PermanentDeleteByUser(th.SystemAdminUser.Id)
+
+		rpost, _ := postAndCheck(t, client, &model.Post{ChannelId: th.BasicChannel.Id, Message: "testMsgC1"})
+		reply1, _ := postAndCheck(t, th.SystemAdminClient, &model.Post{ChannelId: th.BasicChannel.Id, Message: "testReplyC1", RootId: rpost.Id})
+		reply2, _ := postAndCheck(t, th.SystemAdminClient, &model.Post{ChannelId: th.BasicChannel.Id, Message: "testReplyC1", RootId: rpost.Id})
+		reply3, _ := postAndCheck(t, th.SystemAdminClient, &model.Post{ChannelId: th.BasicChannel.Id, Message: "testReplyC1", RootId: rpost.Id})
+
+		checkThreadListReplies(t, th, th.Client, th.BasicUser.Id, 3, 1, nil)
+
+		_, resp, err := th.Client.UpdateThreadReadForUser(th.BasicUser.Id, th.BasicTeam.Id, rpost.Id, reply3.CreateAt+1)
+		require.NoError(t, err)
+		CheckOKStatus(t, resp)
+
+		checkThreadListReplies(t, th, th.Client, th.BasicUser.Id, 0, 1, nil)
+
+		_, resp, err = th.Client.SetThreadUnreadByPostId(th.BasicUser.Id, th.BasicTeam.Id, rpost.Id, reply1.Id)
+		require.NoError(t, err)
+		CheckOKStatus(t, resp)
+
+		checkThreadListReplies(t, th, th.Client, th.BasicUser.Id, 3, 1, nil)
+
+		_, resp, err = th.Client.SetThreadUnreadByPostId(th.BasicUser.Id, th.BasicTeam.Id, rpost.Id, reply2.Id)
+		require.NoError(t, err)
+		CheckOKStatus(t, resp)
+
+		checkThreadListReplies(t, th, th.Client, th.BasicUser.Id, 2, 1, nil)
+
+		_, resp, err = th.Client.SetThreadUnreadByPostId(th.BasicUser.Id, th.BasicTeam.Id, rpost.Id, reply3.Id)
+		require.NoError(t, err)
+		CheckOKStatus(t, resp)
+
+		checkThreadListReplies(t, th, th.Client, th.BasicUser.Id, 1, 1, nil)
+	})
 }
 
 func TestMarkThreadUnreadMentionCount(t *testing.T) {