Fix serialization of SignedUrl

An annotation was missing to include the object_name in the serialization.

src/Bundle/ChillDocStoreBundle/AsyncUpload/SignedUrl.php

@@ -21,6 +21,7 @@ readonly class SignedUrl
         #[Serializer\Groups(['read'])]
         public string $url,
         public \DateTimeImmutable $expires,
+        #[Serializer\Groups(['read'])]
         public string $object_name,
     ) {}