What does "callback" & "transport" do ?
The docs say that  
> callback - relative route or absolute URL to receive the response data /hello | https://site.com/hey ...`

I have probably done something wrong, but it doesn't seem to ever redirect to that url. At first I thought  it would set the `redirect_uri` for the oauth service which it doesn't, and after authenticating and getting redirected to `redirect_uri` it also doesn't redirect to the specified `url`.

Similar issue with `transport`, the `redirect_url` in my case receives all data per query strings, despite having transport set to `session`. 

I am sorry if I didn't configure it correctly 

```js
app.use(
	grant.express({
		defaults: {
			origin: 'http://localhost:5050',
			transport: 'session',
			prefix: '/oauth',
			state: true,
		},
		google: {
			key: googleKey,
			secret: googleSecret,
			scope: ['openid'], // ['openid', 'profile', 'email'],
			nonce: true,
			custom_params: { access_type: 'offline' },
			callback: '/hi',
			redirect_uri: 'http://localhost:5050/googleCallback',
			transport: 'session',
		},
	})
);
```

When I set the `redirect_uri` to the schema specified in the docs `[origin][prefix]/[provider]/callback` (http://localhost:5050/oauth/google/redirect) it just loops back infinitely to the "select account" screen.  