Compatibility with Symfony 6 & PHP 8

[shavounet]

I'm preparing the work to migrate some projects using this bundle to Symfony 6 & PHP 8.

Here are my notes to enable compatibility.

• allow php ^8.0.
• allow symfony/config ^6.0.
• allow symfony/dependency-injection ^6.0. Usage is not huge, but I don't know if there's deprecated code usage.
• allow symfony/event-dispatcher ^6.0. It should probably be fine because I didn't find any call to dispatch
• allow symfony/http-foundation ^6.0.
• allow symfony/http-kernel ^6.0.
• allow symfony/options-resolver ^6.0.
• annotations should probably be converted to PHP8 attributes. Add documentation (or even better, a Rector rule, see this example)
  • once done, we can probably remove doctrine/annotations dependency