fix : use custom EnvironmentCreateProcessor to properly add environments

API Platform's default sub-resource POST was replacing instead of adding.
Custom processor with read:false + Link + manual persist fixes this.

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

src/Entity/Environment.php

@@ -10,6 +10,7 @@ use ApiPlatform\Metadata\Link;
 use ApiPlatform\Metadata\Patch;
 use ApiPlatform\Metadata\Post;
 use App\Repository\EnvironmentRepository;
+use App\State\EnvironmentCreateProcessor;
 use App\State\MaintenanceToggleProcessor;
 use Doctrine\Common\Collections\ArrayCollection;
 use Doctrine\Common\Collections\Collection;
@@ -23,7 +24,9 @@ use Symfony\Component\Serializer\Attribute\Groups;
             uriVariables: [
                 'slug' => new Link(toProperty: 'application', fromClass: Application::class, identifiers: ['slug']),
             ],
+            read: false,
             security: "is_granted('ROLE_ADMIN')",
+            processor: EnvironmentCreateProcessor::class,
         ),
         new Patch(
             security: "is_granted('ROLE_ADMIN')",

src/State/EnvironmentCreateProcessor.php

@@ -0,0 +1,44 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\State;
+
+use ApiPlatform\Metadata\Operation;
+use ApiPlatform\State\ProcessorInterface;
+use App\Entity\Environment;
+use App\Repository\ApplicationRepository;
+use Doctrine\ORM\EntityManagerInterface;
+use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
+
+final readonly class EnvironmentCreateProcessor implements ProcessorInterface
+{
+    public function __construct(
+        private ApplicationRepository $applicationRepository,
+        private EntityManagerInterface $entityManager,
+    ) {}
+
+    /**
+     * @param Environment $data
+     */
+    public function process(mixed $data, Operation $operation, array $uriVariables = [], array $context = []): Environment
+    {
+        $slug = $uriVariables['slug']
+            ?? $context['request']?->attributes->get('slug')
+            ?? $context['request']?->attributes->get('_route_params')['slug']
+            ?? '';
+
+        $application = $this->applicationRepository->findOneBy(['slug' => $slug]);
+
+        if (null === $application) {
+            throw new NotFoundHttpException(sprintf('Application "%s" not found.', $slug));
+        }
+
+        $data->setApplication($application);
+
+        $this->entityManager->persist($data);
+        $this->entityManager->flush();
+
+        return $data;
+    }
+}