FEATURE: Hide deleted posts by default for staff

app/serializers/topic_view_serializer.rb

@@ -39,6 +39,7 @@ class TopicViewSerializer < ApplicationSerializer
              :highest_post_number,
              :last_read_post_number,
              :deleted_by,
+             :has_deleted,
              :actions_summary,
              :expandable_first_post
 
@@ -177,6 +178,14 @@ class TopicViewSerializer < ApplicationSerializer
     result
   end
 
+  def has_deleted
+    object.has_deleted?
+  end
+
+  def include_has_deleted?
+    object.guardian.can_see_deleted_posts?
+  end
+
   def expandable_first_post
     true
   end