Add method to derive private keys outside the expected domain range

[MartinMinkov]

Description

Adds a method to derive public keys from private keys generated from the normal private key range. This sort of behaviour was allowed by the old client_sdk, but new checks added by mina-signer disallowed this action. To offer a backwards-compatible way to derive old private keys, we add a new function which takes the mod of the private key to ensure it's within the domain

Testing Methods

Wrote a little script which used a test keypair which worked with the old client_sdk

import { Client } from "mina-signer";
import * as CodaSDK from "@o1labs/client-sdk";

const client = new Client({
  network: "mainnet",
});

const sk = "..."; // old private key
const pk = "B62qqraqohhfoo8zAbv8UGkZ758mrBRQLw7aKcQuYEd8GfwaqfSXUym"; // corresponding public key used as a test

const oldPk = CodaSDK.derivePublicKey(sk);
const newPk = client.derivePublicKeyUnsafe(sk);

console.log(pk);
console.log(oldPk);
console.log(newPk);
console.log(oldPk === newPk);

[mitschabaude]

I think we should also expose this function on Client, because people need to use it when creating signatures with their out of domain private keys

[MartinMinkov]

sounds good, done!

[mitschabaude]

hey @MartinMinkov I think it was other tools, not our own client sdk, that created out of domain keys, so would reword this comment to definitely not imply that

[mitschabaude]

the old client sdk just accepted them

[MartinMinkov]

good point, fixed!