feat: Test Rector to upgrade code for PHP 8.1

[nlemoine]

Just giving Rector a try :)

Issue

Solution

Impact

Usage Changes

Considerations

Testing

[gchtr]

Just to understand this correctly: We would use this once we move to PHP 8.1 as a minimum required version?

[Levdbas]

would use this once we move to PHP 8.1 as a minimum required version?

I think we could run this from time to time when we have a new release to see if we introduced new code that could be modernized, right @nlemoine ?

[nlemoine]

I think we could run this from time to time when we have a new release to see if we introduced new code that could be modernized, right @nlemoine ?

Actually, since there is a rector task for GrumPHP, we should run this at every commit, avoiding the need for "modernizing" the code base from time to time.

[coveralls]

coverage: 88.006% (+0.3%) from 87.677%
when pulling 2e1fe0a on feat-rector
into 66e92a5 on 2.x.