public Concert(string name, TicketQuantity seatingCapacity)
 {
     Id              = Guid.NewGuid().ToString();
     Name            = name;
     SeatingCapacity = seatingCapacity;
     TicketsSold     = 0;
 }
        public Result <Tickets> IssueTickets(TicketQuantity quantity)
        {
            if (TicketsSold + quantity > SeatingCapacity)
            {
                return(Result.Failure <Tickets>(Errors.NoEnoughTickets));
            }

            TicketsSold += quantity;
            return(Result.Success(new Tickets(this, quantity)));
        }