Добавление enum в миграцию Yii2

Рассмотрим добавление enum на примере простой миграции

<?php

use yii\db\Migration;
use common\components\notifier\Recipients;

/**
* Handles the creation of table `recipients`.
*/
class m191025_122536_create_recipients_table extends Migration
{
    /**
    * @inheritdoc
    */
    public function safeUp()
    {
        $this->createTable('recipients', [
            'id' => $this->primaryKey(),
            'recipientsTypeId' => $this->integer(),
            'recipients' => $this->string()
        ]);

        $this->execute("CREATE TYPE channel as ENUM('email','telegram')");
        $this->addColumn(Recipients::tableName(), 'channel', 'channel NULL DEFAULT NULL');
    }

    /**
    * @inheritdoc
    */
    public function safeDown()
    {
        $this->dropTable('recipients');
        $this->execute('DROP TYPE channel');
    }
}