upgrade to Symfony 6.4

What does this MR do?

Moves the project to Symfony 6.4 (the current LTS) and updates relevant configuration.

I also went through all the "what's new" articles and implemented some unintrusive improvements where I saw fit.

One major thing for the next upgrade will be FOS REST (which is still maintained), and its use of SensioFrameworkExtraBundle (which is abandoned).

Sensio currently is the only thing we need to keep annotation support on for in our project, and with that come a bunch of deprecation warnings everywhere you go.

This will make an upgrade to 7.0+ later impossible, so we'll need to wait for a new FOS REST release to fix this. Plenty of time for them to fix that though, 6.4 is supported until ~2027 😄

How confident are you it won't break things if deployed?

not 100%, though if the tests pass i'm confident enough for beta. After all, this does not change any business logic ;)

Links to related issues

How to test

Screenshots (if applicable)

Checklist

• added a test, or explain why one is not needed/possible...
• no unrelated changes
• asked someone for a code review
• set a "for:" label to indicate who will be affected by this change
• added to the next milestone (see https://gitlab.com/foodsharing-dev/foodsharing/-/milestones, unless it has a "for:Dev" label)
• added an entry to CHANGELOG.md
• added a short text in the release notes to /release-notes/YYYY-MM.md
• Once your MR has been merged, you are responsible to create a testing issue in the Beta Testing forum: https://foodsharing.de/region?bid=734&sub=forum. Please change the MRs label to "state:Beta testing".
  • Consider writing a detailed description in German.
  • Describe in a few sentences, what should be tested from a user perspective.
  • Also mention different settings (e.g. different browsers, roles, ...) how this change can be tested.
  • Be aware, that also non technical people should understand.