* Pass PHPStan level 8
And prepare for PHPStan level 9 https://phpstan.org/user-guide/rule-levels
* Revert wrong replace in comment
* Fix PHPStan level 8
* Update PHPStan and other dev dependencies
* Remove obsolete comment
* noVariableVariables and towards bleedingEdge
https://github.com/phpstan/phpstan-strict-ruleshttps://phpstan.org/blog/what-is-bleeding-edge
* More bleedingEdge
* A bit more PHPStan level 9
* More PHPStan level 9
* Prepare for booleansInConditions
Ignore int and null
* Revert wrong line
* More fixes
* Fix keep_max_n_unread
* Stricter attribute functions
* Stricter callHooks and more PHPStan level 9
* More typing
* A tiny more