Retrieve a broadcast's engagement report

Delivery and engagement for a sending or sent broadcast: unique and total opens and clicks, bounces, complaints, and unsubscribes with rates in percent (open and click rates are over delivered messages), the same by inbox provider, clicks per link, first opens and clicks hour by hour, and the workspace's average over its previous five sent broadcasts. Opens and clicks that looked automated (security scanners, link previews, privacy prefetching, data-center networks) are counted in machine and left out of every other number, so opens remain an estimate. remaining is how many people in a limited audience have not been sent it yet. Returns 409 for a draft.