Tag controller service

This prevents it from being removed as a private service during container optimization.

Author: MalteWunsch

Resources/config/guide.xml

@@ -7,6 +7,7 @@
 
         <service id="Webfactory\ShortcodeBundle\Controller\GuideController">
             <argument><!-- shortcode description placeholder argument --></argument>
+            <tag name="controller.service_arguments"/>
         </service>
 
     </services>