Reply to a change request

Replies to a reviewer change request on a registration in changes_requested state: a note, hosted document URLs (from POST /v1/sms/opt-in-proof), or both, sent together. The registration returns to requested (back in review) — no need to resubmit the whole registration. To change the submitted brand/campaign fields themselves, resubmit via POST /v1/sms/registrations with resubmitRequestId instead.