Gets applicable discounts for a transaction. The discounts are categorized as
1) Transaction-level discounts: Applied on the whole transaction. For example, if the transaction is for $100, the discount is applied by percentage or amount to the whole transaction amount. This category includes tier-specific discounts.
2) Item-level discounts: Applied on specific SKU so that discount percentage or amount is applied to specific product (regardless of the quantity).
3) Miscellaneous discounts - This category captures all other types of discounts.