use Symfony\Component\HttpFoundation\Response;
use ApiPlatform\Metadata\Operation;
use ApiPlatform\State\ProcessorInterface;

class CustomPostProcessor implements ProcessorInterface
{
    public function process($data, Operation $operation, array $uriVariables = [], array $context = [])
    {
        // Do your data persistence logic here
        // ...

        return new Response(
            json_encode(['message' => 'Resource created successfully']),
            Response::HTTP_CREATED, // 201
            ['Content-Type' => 'application/json']
        );
    }
}