public static String toBase64EncodedX25519PrivateKey(XECPrivateKey privateKey) {
        return Base64.getUrlEncoder().withoutPadding().encodeToString(toRawX25519PrivateKeyBytes(privateKey));
    }
Returns the bytes representing the BigInteger of the X25519 public key EC point U coordinate
security-utils/src/main/java/com/yahoo/security/KeyUtils.java