Computes the Vonage signed-request signature (uppercased hex HMAC-SHA256) over the sorted params.
Exported so tests construct a known-good vector and the live router can sign/verify without duplicating
the concat rule. The sig param is excluded from the signed set.
Computes the Vonage signed-request signature (uppercased hex HMAC-SHA256) over the sorted params. Exported so tests construct a known-good vector and the live router can sign/verify without duplicating the concat rule. The
sigparam is excluded from the signed set.