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/retrylayer/retrylayer.go

@@ -3703,32 +3703,11 @@ func (s *RetryLayerDraftStore) GetDraftsForUser(userID string, teamID string) ([
 
 }
 
-func (s *RetryLayerDraftStore) Save(d *model.Draft) (*model.Draft, error) {
+func (s *RetryLayerDraftStore) Upsert(d *model.Draft) (*model.Draft, error) {
 
 	tries := 0
 	for {
-		result, err := s.DraftStore.Save(d)
-		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 *RetryLayerDraftStore) Update(d *model.Draft) (*model.Draft, error) {
-
-	tries := 0
-	for {
-		result, err := s.DraftStore.Update(d)
+		result, err := s.DraftStore.Upsert(d)
 		if err == nil {
 			return result, nil
 		}