public void Extend(DateTime? newDateOfExpiration, decimal value)
 {
     var @event = new TimeAndMaterialJobOrderExtendedEvent(
         this.Id,
         newDateOfExpiration,
         value
     );
     RaiseEvent(@event);
 }
 public void Apply(TimeAndMaterialJobOrderExtendedEvent evt)
 {
     this.DateOfExpiration = evt.NewDateOfExpiration;
     this.Value = new PositiveMoney(evt.Value, this.Value.Currency);
 }