new server not crashed if send bad token

[OsirisAnubiz]

Now if you sand token that not contained on Storage, server not crashed.

There are several points of contention.

1. If Storage did not find a session by key. Pass error to callback or pass undefined?

Now. (pass error)

if (err) {
  callback(err);
  return;
}

Maybe return undefined more correct? It's make Storage more like look on Map.

if (err) {
  callback(null, undefined);
  return;
}

2. Maybe should drop "getIntsance". Because this method, it only creates a client with a session.

If it was not possible to create a client, then it cannot be passed to the handler, then you need to respond with an empty page.
Now

try {
  const client = await Client.getInstance(req, res);
} catch {
  res.statusCode = INVALID_TOKEN_CODE;
  res.end();
  return;
}

More correct?

const client = new Client(req, res);
try {
  await Session.restore(client)
} catch {
  ???????
}