FEATURE: Add small action post to indicate forwarded email

This happens only when the sender of the email didn't write anything in their email.

lib/email/receiver.rb

@@ -844,7 +844,7 @@ module Email
                                           embedded_user: lambda { find_or_create_user(email, display_name) })
       return false unless post
 
-      if post&.topic
+      if post.topic
         # mark post as seen for the forwarder
         PostTiming.record_timing(user_id: user.id, topic_id: post.topic_id, post_number: post.post_number, msecs: 5000)
 
@@ -859,6 +859,8 @@ module Email
                        topic: post.topic,
                        post_type: post_type,
                        skip_validations: user.staged?)
+        else
+          post.topic.add_small_action(user, "forwarded")
         end
       end