Approve a scheduled message pending review

Approves a scheduled message that is pending review (see the pending_review property), on behalf of a user with permission to review messages.

If the message has a scheduled time, approval allows it to be sent at that time, and the updated scheduled message is returned. If it has no scheduled time (it was held from an immediate send), approval sends it right away and returns {"id", "approved": true, "sent": true} plus either broadcast_id (multiple recipients) or message_id (a single message, sent without a broadcast), along with the url of the sent broadcast or message.

When the organization requires the user's confirmation for this application's AI-initiated actions, this method is confirmation-gated like the send methods: approval must come from a person, via an in-session confirmation (such as a confirmation prompt shown by the client) or the web approval link included in the refusal. Applications allowed to act without confirmation may approve messages held by the volume-based review thresholds.