delete_message_backend: Add `durable=True` to the outermost transaction.

This commit adds 'durable=True' to the outermost transaction
in 'delete_message_backend'.

It also adds 'savepoint=False' to inner transaction.atomic
decorator to avoid creating savepoint.

This is as a part of our plan to explicitly mark all the
transaction.atomic decorators with either 'savepoint=False' or
'durable=True' as required.

* 'savepoint=True' is used in special cases.

zerver/lib/retention.py

@@ -141,7 +141,7 @@ def run_archiving(
     message_count = 0
     while True:
         start_time = time.time()
-        with transaction.atomic():
+        with transaction.atomic(savepoint=False):
             archive_transaction = ArchiveTransaction.objects.create(type=type, realm=realm)
             new_chunk = move_rows(
                 Message,
@@ -396,6 +396,7 @@ def archive_stream_messages(
     logger.info("Done. Archived %s messages.", message_count)
 
 
+@transaction.atomic(durable=True)
 def archive_messages(chunk_size: int = MESSAGE_BATCH_SIZE) -> None:
     logger.info("Starting the archiving process with chunk_size %s", chunk_size)
 

zerver/views/message_edit.py

@@ -167,7 +167,7 @@ def validate_can_delete_message(user_profile: UserProfile, message: Message) ->
     return
 
 
-@transaction.atomic
+@transaction.atomic(durable=True)
 @typed_endpoint
 def delete_message_backend(
     request: HttpRequest,