POSTs body as JSON to url with the given auth_header. Retries up to 3 times with a 200 ms delay between attempts on network error. Each attempt is bounded by a connect timeout and a receive timeout so a hung intake can never block the caller indefinitely. Returns {:ok, response} or {:error, reason}.

The x-epb-sdk value sent on every call to intake: elixir/<version>, the version of this library as loaded (sc-1463). intake ignores it today; it is there so intake can record the oldest version seen per credential for the move gate. That gate's minimum Elixir version is the release that turns derive_base_url_from_client_id on by default, not the one that added this header: with the option at its default, this version keeps calling in.endpointblank.com after its organization moves.