SipDisconnectReason

Why the call disconnected: the SIP status code and reason phrase from the final response / BYE (e.g. 486 "Busy Here", 401 "Unauthorized", 200 "OK" for a normal hangup). Emitted alongside the DISCONNECTED status so a client can tell busy / declined / auth-failure / unreachable / far-end BYE / local hangup apart, and stop redialling a code that can never succeed.