MM-49564: Drafts upsert in the Store vs App layer (#22530)

* MM-49564: Upsert in the Store vs App layer

Refactor drafts so that Upserting a draft would happen in the DB and not
in the app layer.

* Fixes mocks

* Fixes tests

* Fixes translations

* Fixes tests

* Update tests

* Fixes tests

* Addresses review comments

- renames Save => Upsert
- removes Sleep from tests

* Fixes flaky test

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

server/channels/store/timerlayer/timerlayer.go

@@ -3038,10 +3038,10 @@ func (s *TimerLayerDraftStore) GetDraftsForUser(userID string, teamID string) ([
 	return result, err
 }
 
-func (s *TimerLayerDraftStore) Save(d *model.Draft) (*model.Draft, error) {
+func (s *TimerLayerDraftStore) Upsert(d *model.Draft) (*model.Draft, error) {
 	start := time.Now()
 
-	result, err := s.DraftStore.Save(d)
+	result, err := s.DraftStore.Upsert(d)
 
 	elapsed := float64(time.Since(start)) / float64(time.Second)
 	if s.Root.Metrics != nil {
@@ -3049,23 +3049,7 @@ func (s *TimerLayerDraftStore) Save(d *model.Draft) (*model.Draft, error) {
 		if err == nil {
 			success = "true"
 		}
-		s.Root.Metrics.ObserveStoreMethodDuration("DraftStore.Save", success, elapsed)
-	}
-	return result, err
-}
-
-func (s *TimerLayerDraftStore) Update(d *model.Draft) (*model.Draft, error) {
-	start := time.Now()
-
-	result, err := s.DraftStore.Update(d)
-
-	elapsed := float64(time.Since(start)) / float64(time.Second)
-	if s.Root.Metrics != nil {
-		success := "false"
-		if err == nil {
-			success = "true"
-		}
-		s.Root.Metrics.ObserveStoreMethodDuration("DraftStore.Update", success, elapsed)
+		s.Root.Metrics.ObserveStoreMethodDuration("DraftStore.Upsert", success, elapsed)
 	}
 	return result, err
 }