mod reports: enable reporting for members, add dmail reporting.

* Add ability to report dmails.
* Enable reports for comments, forum posts, and dmails.
* Allow Members to send reports.
* Don't allow users to report the same thing twice.

app/models/post.rb

@@ -1782,8 +1782,4 @@ class Post < ApplicationRecord
 
     save
   end
-
-  def viewable_moderation_reports
-    CurrentUser.is_moderator? ? moderation_reports.recent : []
-  end
 end