we need to integrate publicKey with message into TransactionAuthenticator for sign.
the benifit is that we can later decode and get the signed address from the publicKey.

1. add 2 functions in utils/sign: encodeTransactionAuthenticator / decodeTransactionAuthenticator
2. add 2 test cases:
   yarn test:unit src/utils/sign.spec.ts --testNamePattern="encode"
   yarn test:unit src/utils/sign.spec.ts --testNamePattern="sign"