Add voter for ExportGeneration stored object authorization

Introduces `ExportGenerationStoredObjectVoter` to handle permissions for stored objects linked to export generations. Implements entity association retrieval in `ExportGenerationRepository` by adhering to `AssociatedEntityToStoredObjectInterface`.

src/Bundle/ChillMainBundle/Repository/ExportGenerationRepository.php

@@ -11,17 +11,30 @@ declare(strict_types=1);
 
 namespace Chill\MainBundle\Repository;
 
+use Chill\DocStoreBundle\Entity\StoredObject;
+use Chill\DocStoreBundle\Repository\AssociatedEntityToStoredObjectInterface;
 use Chill\MainBundle\Entity\ExportGeneration;
 use Doctrine\Bundle\DoctrineBundle\Repository\ServiceEntityRepository;
 use Doctrine\Persistence\ManagerRegistry;
 
 /**
  * @extends ServiceEntityRepository<ExportGeneration>
+ *
+ * @implements AssociatedEntityToStoredObjectInterface<ExportGeneration>
  */
-class ExportGenerationRepository extends ServiceEntityRepository
+class ExportGenerationRepository extends ServiceEntityRepository implements AssociatedEntityToStoredObjectInterface
 {
     public function __construct(ManagerRegistry $registry)
     {
         parent::__construct($registry, ExportGeneration::class);
     }
+
+    public function findAssociatedEntityToStoredObject(StoredObject $storedObject): ?ExportGeneration
+    {
+        return $this->createQueryBuilder('e')
+            ->where('e.storedObject = :storedObject')
+            ->setParameter('storedObject', $storedObject)
+            ->getQuery()
+            ->getOneOrNullResult();
+    }
 }