Fix code quality issues reported by GitlabCI

Postponing because most remaining issues in phpstan and phpunit are related to these other issues

Tests are failing in CI

@duaelfr can you update the merge request target to branch 3.0.x? This option is only available for the creator (or maintainers)

@idebr Of course! Sorry for the mistake (twice in a row, I must have been tired this day...)

Let's merge this and fix whatever is missing afterwards, thanks all for the hard work on this one.

Automatically closed - issue fixed for 2 weeks with no activity.