Check if quiz configuration settings are working as expected

Configuration settings can be found at admin/config/quiz/* paths. Need to ensure whether these are working as expected.

For instance - Delete results when a user is deleted, Display name, etc.

In connection to this - it seems _quiz_get_quiz_name() returns empty value (unless configuration form is saved at least once). As result configuration menus Quiz configuration, Quiz form configuration and Quiz results are read as configuration, form configuration and results respectively.

function _quiz_get_quiz_name() {
  // @todo: remove all the quiz_name stuff? Isn't there better ways to do this?
  return \Drupal::config('quiz.settings')->get('quiz_name');
}

Perhaps no default value is set.