fix : correct Link uriVariables for environment POST endpoint

Use toProperty + identifiers instead of fromProperty to resolve
application slug correctly.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/Entity/Environment.php

@@ -21,7 +21,7 @@ use Symfony\Component\Serializer\Attribute\Groups;
         new Post(
             uriTemplate: '/applications/{slug}/environments',
             uriVariables: [
-                'slug' => new Link(fromClass: Application::class, fromProperty: 'environments'),
+                'slug' => new Link(toProperty: 'application', fromClass: Application::class, identifiers: ['slug']),
             ],
             security: "is_granted('ROLE_ADMIN')",
         ),