This is the discount specific version of the CalculationCodeApply command.
The default implementation for discount calculationUsage creates an
OrderAdjustment object for the Order, and creates an OrderItemAdjustment
object for each of the OrderItems in the list using the
specified MonetaryAmounts. The OrderAdjustmentTaxExempt information for the
OrderItemAdjustments is set as specified by the CalculationCodeTaxExempt
information for the specified CalculationCode.