PHP 8.4 compatibility issue

Problem/Motivation

Module is not compatible with php 8.4 and throwing warning on drush cr.

Steps to reproduce

Deprecated function: Drupal\samlauth\SamlService::reformatConfig(): Implicitly marking parameter $key_repository as nullable is deprecated, the explicit nullable type must be used instead in include() (line 576 of /var/www/html/vendor/composer/ClassLoader.php)

Deprecated function: Drupal\samlauth\SamlService::doLogin(): Implicitly marking parameter $account as nullable is deprecated, the explicit nullable type must be used instead in include() (line 576 of /var/www/html/vendor/composer/ClassLoader.php)

Proposed resolution

Fix php code and make it compatible