Set base representation getControllerName public

All the overrides are already public and things are assuming that the
method just generally is public.

application/src/Api/Representation/AbstractResourceRepresentation.php

@@ -274,7 +274,7 @@ public function getFileUrl($prefix, $name, $extension = null)
      *
      * @return string|null
      */
-    protected function getControllerName()
+    public function getControllerName()
     {
         return null;
     }