OptionalbillingOptionalidHost-app id; defaults to a generated UUID.
Idempotency for the FIRST charge (renewals derive their own keys).
OptionalmetadataSavedPaymentMethod.token / PaymentInfo.savedPaymentMethodToken.
OptionalstartFuture instant = trial / delayed start: nothing is charged now, the first charge happens when chargeDueSubscriptions crosses it. Omitted = charge the first period immediately (customer-present "initial" charge).
AVS data carried on the record and forwarded on EVERY charge (first and renewals) — some PSPs (Paysafe) demand a zip on stored-token charges of browser-tokenized cards.