GHSA-M4W9-HJFW-VWJ4 http4k: `HmacSha256.hash` (despite the `Hmac` naming) computed a plain unkeyed digest; clarified by deprecation in favour of `Sha256.hash` / `Sha256.hmac`

Impact The HmacSha256 class contained two functions: - hashpayload — a plain unkeyed SHA-256 digest. The Hmac prefix in the class name was misleading; this function has no key parameter, so it could never have been an HMAC. - hmacSHA256key, data — a properly keyed HMAC-SHA256. A reader who didn't...