Operations for discounts when retaining existing modifications.
Discounts to add (by template ID).
Discounts to edit (by template ID; server resolves to instance).
remove[ID!]IDs of discount instances to remove.
input RecurringBillingSubscriptionRetainExistingDiscountsInput {
add: [RecurringBillingSubscriptionDiscountInput!]
edit: [RecurringBillingSubscriptionDiscountInput!]
remove: [ID!]
}