The REST update payload ITwilioRestLike calls(sid).update accepts (the subset we use).
calls(sid).update
Optional
New call status — 'completed' ends the call.
'completed'
Replacement TwiML — used for transfer (<Dial>…) and the goodbye-and-hang-up (<Say>…<Hangup/>).
<Dial>…
<Say>…<Hangup/>
The REST update payload ITwilioRestLike
calls(sid).updateaccepts (the subset we use).