public static int Row(this IBoardingPass boardingPass)
        {
            if (boardingPass == null)
            {
                throw new ArgumentNullException(nameof(boardingPass));
            }

            if (boardingPass.IsValid() == false)
            {
                throw new ArgumentException(nameof(boardingPass));
            }

            return(CalculateRowPosition(boardingPass));
        }
        public static int SeatId(this IBoardingPass boardingPass)
        {
            if (boardingPass == null)
            {
                throw new ArgumentNullException(nameof(boardingPass));
            }

            if (boardingPass.IsValid() == false)
            {
                throw new ArgumentException(nameof(boardingPass));
            }

            // (row x 8) + col
            return((Row(boardingPass) * 8) + Column(boardingPass));
        }