Authorizations
Bearer authentication header of the form Bearer <token>, where <token> is your auth token.
Body
Create payment for subscription onetime addon purchase
AddonId, id of one-time addon, the new payment will created base on the addon's amount'
Quantity, quantity of the new payment which one-time addon purchased
apply promo credit or not
apply promo credit amount, auto compute if not specified
CancelUrl, back to cancelUrl if user cancel the payment
Amount of discount
DiscountCode
Percentage of discount, 100=1%, ignore if discountAmount specified
GatewayId, use user's gateway if not provide
Gateway Payment Type
Metadata,custom data
ReturnUrl, the addon's payment will redirect based on the returnUrl provided when it's back from gateway side
SubscriptionId, id of subscription which addon will attached, either SubscriptionId or UserId needed, The only one active subscription of userId will attach the addon
TaxPercentage,1000 = 10%, default user's taxPercentage if not specified
UserId, either SubscriptionId or UserId needed, The only one active subscription will update if userId provide instead of subscriptionId

