Implement context-specific voters for all current entities that can be linked to a document

For reusability an AbstractStoredObjectVoter was created and a StoredObjectVoterInterface.
A WorkflowDocumentService checks whether the StoredObject is involved in a workflow.

src/Bundle/ChillEventBundle/Entity/Event.php

@@ -31,7 +31,7 @@ use Symfony\Component\Validator\Constraints as Assert;
 /**
  * Class Event.
  */
-#[ORM\Entity(repositoryClass: \Chill\EventBundle\Repository\EventRepository::class)]
+#[ORM\Entity]
 #[ORM\HasLifecycleCallbacks]
 #[ORM\Table(name: 'chill_event_event')]
 class Event implements HasCenterInterface, HasScopeInterface, TrackCreationInterface, TrackUpdateInterface