提交的数据

$_GET = [
    'r' => 'site/login',
];

$_POST = [
    '_csrf' => 'WjgxM0tfa3YxQn1rcg4vHioLVlt.EjhOAnFVR3MuXgQ7WkNmBwofIg==',
    'LoginForm' => [
        'username' => 'admin',
        'password' => 'admin',
        'rememberMe' => '1',
    ],
    'login-button' => '',
];

yii2 处理管理员登陆部分的代码：

#/var/www/example.com/public_html/yii/backend/controllers/SiteController.php
    public function actionLogin()
    {
        if (!\Yii::$app->user->isGuest) {
            return $this->goHome();
        }

        $model = new LoginForm();
        if ($model->load(Yii::$app->request->post()) && $model->login()) {
            return $this->goBack();
        } else {
            return $this->render('login', [
                'model' => $model,
            ]);
        }
    }

但是我并没有user表，这里是backend，管理员登陆部分，对应的表是admin，结构。

mysql> desc admin;
+-------+------------------+------+-----+---------+-------+
| Field | Type             | Null | Key | Default | Extra |
+-------+------------------+------+-----+---------+-------+
| id    | int(10) unsigned | NO   |     | NULL    |       |
| name  | char(30)         | NO   |     |         |       |
| pwd   | char(32)         | NO   |     |         |       |
| email | char(30)         | NO   |     |         |       |
+-------+------------------+------+-----+---------+-------+
4 rows in set (0.03 sec)

mysql> select * from admin;
+----+---------+----------------------------------+-------+
| id | name    | pwd                              | email |
+----+---------+----------------------------------+-------+
|  1 | admin   | b9840270f7f4ed699ccc93cc09914d21 |       |
+----+---------+----------------------------------+-------+
1 row in set (0.00 sec)

yii2 他默认的都是user表，可我并没有user表。
我现在提交了用户名和密码，该如何修改actionLogin里面的代码才最合适。