add manager api

backend/config/main.php

@@ -72,7 +72,7 @@ return [
     'components' => [
         'request' => [
             'csrfParam' => '_csrf-backend',
-            'baseUrl' => '', // /secure
+            'baseUrl' => '/secure', // /secure
             'parsers' => [
                 'application/json' => 'yii\web\JsonParser',
                 'text/xml' => 'yii/web/XmlParser',

backend/modules/employee/views/manager/_form.php

@@ -16,7 +16,8 @@ use kartik\select2\Select2;
 
     <?= $form->field($model, 'user_id')->widget(Select2::className(),
         [
-            'data' => User::find()->select(['username', 'id'])->indexBy('id')->column(),
+            'data' => User::find()->select(['username', 'user.id'])
+                ->joinWith('manager')->where(['manager.user_id' => null])->indexBy('user.id')->column(),
             'options' => ['placeholder' => '...','class' => 'form-control'],
             'pluginOptions' => [
                 'allowClear' => true