SDK improvements

- Using Session for storing user
- Getting user from Auth0
- Storing tokens object in session
- Removed HTTPClient in favor of Resty
- Simplified code for Filter and Callback handler
HTTPClient is a monster and old. It also has the worst interface for doing requests ever. It needs 100 different classes to do a simple post. This is simple and returns JSon by one without using Jackson or parsing entire stream or anything like that.

This is also more optimized than previous code since it doesn't parse all string to then transform to JSon. JsonResource uses the InputStream from the request