Feature/php8 perf

[Chris53897]

Superseeds #57
With a possible solution for #46

Add a additional paramter if the event should be unique.
https://github.com/tattali/CalendarBundle/compare/master...Chris53897:feature/php8-perf?expand=1#diff-e29df28b700bc5afb6adaf9697c4489ddb60b252021b353e5d078af1f9e73a9eR44

Tests:
https://github.com/tattali/CalendarBundle/compare/master...Chris53897:feature/php8-perf?expand=1#diff-176744ef8dbdd61a7010c8f3dcb08b6e4647e4dfb8d9276f764c1c6131c9c41cR46

This is a BC Break if the default Value is false.
But maybe this is new major anyways.

For isset or array_key_exists an unique-Field like id has to be mandatory.
But this is a BC Break as well.

[tattali]

Hi, can you rebase from master and show only changes of this pull request.
Thanks!

[Chris53897]

@tattali I merged master into this. (more on accident, but almost the same effect if you squash and merge buton it github.