OptionalappOptional client app/source label stored in Stripe metadata.
OptionaldeviceOptional opaque host-application context forwarded only when provided.
OptionalredirectPost-checkout redirect target. Defaults to 'web'.
OptionalstartWhether to start a free trial when the account is eligible. Defaults to the
server's behavior when omitted. Pass false to explicitly subscribe now
with no trial even if the account is otherwise eligible — the value is sent
verbatim so the backend honors the "no trial" intent.
Options for
AccountApi.createSubscriptionCheckout.