fix(openapi): define items type for HydraCollectionBaseSchema hydra:member (#7419)

Co-authored-by: Thibaut Cholley <[email protected]>

Author: Cafeine42

src/Hydra/JsonSchema/SchemaFactory.php

@@ -190,6 +190,7 @@ public function buildSchema(string $className, string $format = 'jsonld', string
                 'type' => 'object',
                 'required' => [
                     $hydraPrefix.'member',
+                    'items' => ['type' => 'object'],
                 ],
                 'properties' => [
                     $hydraPrefix.'member' => [