Symfony 7 Compatibility

[KamiYang]

Symfony did release their new major version 7 in November 2023 and we should check if we can support this version out-of-the-box or if not, what has to be achieved to be able to support Symfony 7.

Upgrade guide provided by Symfony: https://github.com/symfony/symfony/blob/7.0/UPGRADE-7.0.md