/**
  * Returns a List of Users
  */
 public function actionIndex()
 {
     $form = new \humhub\modules\admin\models\forms\AuthenticationSettingsForm();
     if ($form->load(Yii::$app->request->post()) && $form->validate() && $form->save()) {
         Yii::$app->getSession()->setFlash('data-saved', Yii::t('AdminModule.controllers_SettingController', 'Saved'));
     }
     // Build Group Dropdown
     $groups = [];
     $groups[''] = Yii::t('AdminModule.controllers_SettingController', 'None - shows dropdown in user registration.');
     foreach (\humhub\modules\user\models\Group::find()->all() as $group) {
         if (!$group->is_admin_group) {
             $groups[$group->id] = $group->name;
         }
     }
     return $this->render('authentication', array('model' => $form, 'groups' => $groups));
 }