public static HKDF unsaltedExtractedFrom(byte[] ikm) {
        return extractedFrom(ALL_ZEROS_SALT, ikm);
    }
Creates and returns a new <em>unsalted</em> HKDF instance extracted from the given key.

<p>Prefer using the salted {@link #extractedFrom(byte[], byte[])} method if possible.</p>

@param ikm secret initial Input Keying Material value.
@return a new HKDF instance ready for deriving keys based on the IKM and an all-zero salt.
security-utils/src/main/java/com/yahoo/security/HKDF.java