Class RingCentralTelephonyService

Best-effort teardown of the SIP registration (server shutdown).

Whether the SIP line can be expected to receive calls. Start() swallows a registration failure (it only logs), so without this the extension would report healthy while every inbound call went unanswered. Pending is healthy only until REGISTRATION_DEADLINE_MS; a failure is unhealthy with its reason.

Resolves the dialed DID to a pinned agent and starts an INBOUND bridge session.

Places an OUTBOUND call from a given agent identity to a destination number, after the shared outbound gate (agent permission, destination policy, rate limit) has authorized it.

Creates + registers the shared SIP softphone and wires inbound INVITE handling.