Refactor workflow handlers and update comments

Changes include class refactoring for Workflow handlers, using `readonly` and better indentation in constructors for better readability. In addition, outdated comments are removed. Also, entity workflow handlers now implement the EntityWorkflowHandlerInterface type for better type safety.

src/Bundle/ChillMainBundle/Workflow/EntityWorkflowHandlerInterface.php

@@ -14,6 +14,9 @@ namespace Chill\MainBundle\Workflow;
 use Chill\MainBundle\Entity\User;
 use Chill\MainBundle\Entity\Workflow\EntityWorkflow;
 
+/**
+ * @template T of object
+ */
 interface EntityWorkflowHandlerInterface
 {
     /**
@@ -25,6 +28,9 @@ interface EntityWorkflowHandlerInterface
 
     public function getEntityTitle(EntityWorkflow $entityWorkflow, array $options = []): string;
 
+    /**
+     * @return T|null
+     */
     public function getRelatedEntity(EntityWorkflow $entityWorkflow): ?object;
 
     public function getRelatedObjects(object $object): array;