SubscriptionExtendedBasenamestringOptionalThe name of the subscription.start_datestring<DateTimeWithZone>OptionalDate and time in ISO 8601 format.Formatdate-timeend_datestring<DateTimeWithZone>OptionalDate and time in ISO 8601 format.Formatdate-timeexternal_customer_idstringRequiredExternal reference to the customerMatch^[a-zA-Z0-9_-]*$external_idstring<SubscriptionExternalId>RequiredThe subscription external unique identifier supplied by client. Must contain only alphanumeric characters, underscores, and hyphens.Match^[a-zA-Z0-9_-]*$plan_codestringRequiredThe plan codebilling_timeenum<BillingTime>OptionalThe billing time for the subscription, which can be set as either anniversary or calendarDefault"CALENDAR"Value in"CALENDAR" | "ANNIVERSARY"