Get a Message's Approval Round

The latest approval round for a held calendar message, as the signed-in user sees it on the approval page: the round and its decisions, the event, the message's send time and segments, every round of the event's approval history, the details (channel, segments with counts, recipients, split), the link_check blocklist results for linked domains, previews (the exact content subscribers would receive), and approver when the user is an approver of the message's publication and can decide. Decide with decide_message_approval using request.id.