This change adds the PHP attribute SensitiveParameter to the secret
holding variables.
See: https://www.php.net/manual/en/class.sensitiveparameter
This feature is only available in PHP 8.2, so the minimum php version
required has been updated.
Github Actions now use PHP 8.2 and 8.3 for the tests.
The checkout action has been updated to v4, too.
Fix issue #118