How do I select between multiple notification channels?

Hi folks

Fairly new to Laravel and slowly building a team invite system. I've read up and Googled as much as I can on how to use Laravel Notifications, but I'm stuck on how to select between multiple notifcation channels (most likely based on user preference setting).

Here's my notification:

namespace App\Notifications\Frontend\Team;

use Illuminate\Bus\Queueable;
use Illuminate\Notifications\Notification;
use Illuminate\Notifications\Messages\MailMessage;

/**
 * Class TeamInvitation.
 */
class TeamInvitation extends Notification
{
    use Queueable;

    /**
     * @var
     */
    protected $team_invite;

    /**
     * TeamInvitation constructor.
     *
     * @param $team_invite
     */
    public function __construct($team_invite)
    {
        $this->team_invite = $team_invite;
    }

    /**
     * Get the notification's delivery channels.
     *
     * @param mixed $notifiable
     *
     * @return array
     */
    public function via($notifiable)
    {

        return ['database', 'mail'];
    }

    /**
     * Get the mail representation of the notification.
     *
     * @param mixed $notifiable
     *
     * @return \Illuminate\Notifications\Messages\MailMessage
     */
    public function toMail($notifiable)
    {
        return (new MailMessage())
            ->subject(app_name().': '.__('exceptions.frontend.auth.confirmation.confirm'))
            ->line(__('strings.emails.auth.thank_you_for_using_app'));
    }

    /**
     * @param $notifiable
     * @return mixed
     */
    public function toDatabase($notifiable)
    {
        return $this->team_invite->toArray();
    }

}

and in my controller I have

$user->notify(new TeamInvitation($team_invite));

Currently works in the sense that notification is created in my database table and and email notification is sense. How would I select which channel to use in my controller?

Thanks