compareSafetyNumber

Compares the safety number of remote with scanned, the payload the other device shows (SafetyNumber.encode). Never changes trust state, also on a match: call markRemoteIdentityVerified once the user confirmed. Throws SecureMessageClientException.InvalidSafetyNumberPayload for a payload that does not decode and SecureMessageClientException.RemoteIdentityNotKnown if nothing is pinned.