public static Notification GigCanceled(Gig gig) => new Notification(NotificationType.GigCanceled, gig);
//private NotificationType gigCanceled;
private Notification(NotificationType type, Gig gig)
{
Gig = gig ?? throw new ArgumentException("Gig cannot be null");
this.Type = type;
DateTime = DateTime.Now;
}