Edit a sent text message

Sends one message from the given session. There is a **single** send endpoint for every kind of message; the discriminated `type` field in the request body chooses which one. **Supported in v1:** `text`, `poll`, `location`, and `contact`. **Not implemented yet:** the media types `image`, `video`, `audio`, `document`, and `sticker` return **501 `not_implemented`** before any WhatsApp call is made. ### Delivery mode (`?async`) - **Synchronous (default, `?async=false`):** the call blocks until WhatsApp acknowledges the send and returns **200** with the final `SendResult`. - **Asynchronous (`?async=true`):** the gateway persists the send to a queue and returns **202** immediately with a queued `SendResult`. The final delivery status arrives later as a `message.status` event on the event stream. ### Idempotency (`Idempotency-Key` header) Supply a stable key to make retries safe: replaying a send with a key already seen for your organization returns the **original** result and does not dispatch a second WhatsApp message. ### Preconditions & errors - Requires the **`send`** capability. - The session must exist, be owned by your organization, and be connected. - **400 `validation_error`** — malformed body or an unsupported/invalid field for the chosen `type`. - **404 `not_found`** — the session does not exist or is not owned by your organization. - **429 `rate_limited`** — over the per-session send rate limit. A synchronous send is rejected with 429; an async send stays queued instead of failing. - **501 `not_implemented`** — a media `type` that is not built yet.