Send a message to a conversation route
Accept one authed message for route_name and run its turn AS the route’s
execution key.
The auth gate authorizes who may SEND; the turn’s own authority is the route’s
execution key, not the caller. Default answer is 202 {message_id, thread_id} with
the answer delivered later by signed callback. With a wait_seconds body field
(clamped here to sync_wait_max_seconds) a turn finishing in time answers 200
with the answer inline and its callback suppressed, so it never double-fires; a turn
still running when the wait elapses falls back to 202.
Authorizations
Path Parameters
Body
The client-facing inbound body of the authed API door
POST /api/conversations/{route_name}/messages.
external_user_id is the caller's handle for the end user: it becomes the
client_address the answer is delivered against and the conversation's thread
key. Frozen.
Response
Success.

