notes: convert internal links to Danbooru to relative urls.

config/danbooru_default_config.rb

@@ -20,11 +20,17 @@ module Danbooru
       "Find good anime art fast"
     end
 
-    # The hostname of the server.
+    # The canonical hostname of the site.
     def hostname
       Socket.gethostname
     end
 
+    # The list of all domain names this site is accessible under.
+    # Example: %w[danbooru.donmai.us sonohara.donmai.us hijiribe.donmai.us safebooru.donmai.us]
+    def hostnames
+      [hostname]
+    end
+
     # Contact email address of the admin.
     def contact_email
       "webmaster@#{server_host}"