Missing require symfony/translation-contracts

[n-valverde]

API Platform version(s) affected: 3.1

Description
Hello,

Creating a fresh Symfony app with require api-platform/core leads to PHP Fatal error: Trait Symfony\Contracts\Translation\TranslatorTrait" not found.

This is caused by the constructor of ApiPlatform\Symfony\EventListener\DeserializeListener, when the translator component is not installed. It is using symfony/translation-contracts as a fallback without actually requiring it or verifying it's installed.

final class DeserializeListener
{
    public function __construct(....., private ?TranslatorInterface $translator = null)
    {
        if (null === $this->translator) {
            $this->translator = new class() implements TranslatorInterface, LocaleAwareInterface {
                use TranslatorTrait; // Offending line
            };
            $this->translator->setLocale('en');
        }
    }

How to reproduce

• Create a new symfony app
• composer require api-platform/core
• Create a resource and try to hit the route

Possible Solution
Add symfony/translation-contracts to composer require or add a pass to ensure there is either the translator component or the contracts available