Add signatureZoneIndex to PdfSignedMessage and related classes

Included signatureZoneIndex for PdfSignedMessage in class definitions, handlers, and serializers to support signature zones. Updated test cases to reflect this new property, ensuring robust validation for handling and serialization.

src/Bundle/ChillDocStoreBundle/Service/Signature/Driver/BaseSigner/PdfSignedMessageHandler.php

@@ -55,6 +55,7 @@ final readonly class PdfSignedMessageHandler implements MessageHandlerInterface
         $this->storedObjectManager->write($storedObject, $message->content);
 
         $signature->setState(EntityWorkflowSignatureStateEnum::SIGNED)->setStateDate($this->clock->now());
+        $signature->setZoneSignatureIndex($message->signatureZoneIndex);
         $this->entityManager->flush();
         $this->entityManager->clear();
     }