Opendistrib/console/migrations/m180312_174327_slug_producer.php

<?php

use yii\db\Migration;
use yii\db\Schema;

class m180312_174327_slug_producer extends Migration {

    public function up() {
        $this->addColumn('etablissement','slug',Schema::TYPE_STRING);
    }

    public function down() {
        $this->dropColumn('etablissement','slug');
    }
}