Support for a new site setting: newuser_spam_host_threshold. If a new user posts a link

to the same host enough tiles, they will not be able to post the same link again.

Additionally, the site will flag all their previous posts with links as spam and they will
be instantly hidden via the auto hide workflow.

lib/discourse.rb

@@ -73,6 +73,12 @@ module Discourse
     end
   end
 
+  # Either returns the system_username user or the first admin.
+  def self.system_user
+    user = User.where(username_lower: SiteSetting.system_username).first if SiteSetting.system_username.present?
+    user = User.admins.order(:id).first if user.blank?
+    user
+  end
 
 private