Using Rack::Proxy to serve multiple React Apps on the same domain.

Link: https://blog.joshsoftware.com/2019/09/03/using-rackproxy-to-serve-multiple-react-apps-on-the-same-domain/

We had 4 React apps running on the local server. All apps were running on different ports because we can not start multiple React Apps on the same port. We had to build a single sign-on server. Out of 4 react apps one will be responsible for managing authentication and based on roles or department redirecting to other apps. The Auth app will get token from Auth API and will store it to local storage, and other apps will be using this token for authentication while calling APIs.