Destroy a SIP line

Destroys the line, not the phone number. The PJSIP endpoint is erased from the telephony switch, any SIP device registered to the line loses its registration, and the line goes deprovisioned — that part is not reversible, and provisioning a line again produces a NEW line whose internal extension is almost certainly different, so every device configured with the old one has to be reconfigured. The external inbound number stays with the company: it only stops routing to this line, keeps its is_default flag and its auto-renewal, and is handed straight back to the next line the company provisions — so the number a customer has published does not change under them. Giving a number up for good is a separate, deliberate act in the dashboard, never a side effect of removing a line. If the intent is only to move the line to somebody else, unbind the recipient instead — that leaves the line itself in place. Operator lines only: this API hands out operator lines and takes back only those. The notification line is the company's single shared trunk for every outbound voice alert and does not come back on its own; webrtc lines belong to a person's browser. Neither is created here, and both answer 422.