adding a default jwt uuid. Refs #513

[ekryski]

Summary

We already supported passing your own jwtid by setting hook.params.jwt.jwtid = myId before an authentication create call or by explicitly calling:

const options = {
  jwt: {
    jwtid: myId
  }
};
app.passport.createJWT(payload, options).then(...

This PR makes it so that by default a uuid is assigned to the jwtid value. This sets us up better so that we can whitelist/blacklist tokens.