fix?

src/Entity/DocumentObject.php

@@ -33,6 +33,7 @@ use Vich\UploaderBundle\Mapping\Annotation as Vich;
             formats: [
                 'multipart' => ['multipart/form-data']
             ],
+            outputFormats: ['json' => ['application/json'], 'jsonld' => ['application/ld+json']],
             controller: CreateDocumentObjectAction::class,
             openapi: new Model\Operation(
                 requestBody: new Model\RequestBody(
@@ -56,8 +57,9 @@ use Vich\UploaderBundle\Mapping\Annotation as Vich;
         ),
         new Delete(),
     ],
+    formats: ['jsonld', 'json'],
     normalizationContext: ['groups' => ['document_object:read']],
-    security: 'is_granted("ROLE_USER")',
+    security: 'is_granted("ROLE_USER")'
 )]
 class DocumentObject
 {