Merge branch 'notifications-query' into 'develop'

Fix notifications query to use the index

See merge request pleroma/pleroma!4058

changelog.d/notifications-index.fix

@@ -0,0 +1 @@
+Fix notifications query which was not using the index properly

lib/pleroma/notification.ex

@@ -88,7 +88,7 @@ def last_read_query(user) do
       where: q.seen == true,
       select: type(q.id, :string),
       limit: 1,
-      order_by: [desc: :id]
+      order_by: fragment("? desc nulls last", q.id)
     )
   end