Laravel Notifications: Multi-Channel Messages

class OrderShipped extends Notification
{
    public function via($notifiable)
    {
        return ['mail', 'database', 'slack'];
    }

    public function toMail($notifiable)
    {
        return (new MailMessage)
            ->line('Your order has shipped!');
    }
}

$user->notify(new OrderShipped($order));

class OrderShipped extends Notification implements ShouldQueue
{
    // Automatically queued
}