Add hint that zoom level is probably required (Close #56).

src/Bundle/Resources/config/listeners.yml

@@ -30,6 +30,8 @@ services:
       - '@netzmacht.contao_toolkit.dca.manager'
       - '@database_connection'
       - '@netzmacht.contao_toolkit.repository_manager'
+      - '@translator'
+      - '@session'
 
   netzmacht.contao_leaflet.listeners.dca.control:
     class: Netzmacht\Contao\Leaflet\Listener\Dca\ControlDcaListener