Optionalbuttons?: ScheduledButtonInput[]Optionalcontent?: stringOptionaldate?: string | nullOptionalembed?: ScheduledEmbedInput | nullOptionaltime?: string | nullHH:mm in UTC, with date.
OptionalwebhookOptionalwebhookOptionalwebhook
One-time messages only: a new send date,
YYYY-MM-DDin UTC (same shape as create). A sent one-time message is switched off rather than deleted; a futuredate+timeturns it back on. Recurring, event and stage messages answer 400.