Cache the trees structures for treeViews used in the sidebar.

src/Repository/UserRepository.php

@@ -37,7 +37,7 @@ use Symfony\Component\Security\Core\User\UserInterface;
  * @method User[]    findAll()
  * @method User[]    findBy(array $criteria, array $orderBy = null, $limit = null, $offset = null)
  */
-class UserRepository extends EntityRepository implements PasswordUpgraderInterface
+class UserRepository extends NamedDBElementRepository implements PasswordUpgraderInterface
 {
     protected $anonymous_user;