title: Redirect to Frontend ( On A Different URL ) after OAuth2 Login
body: <p>I am trying to setup my application as follow : </p>
  
  <ol>
  <li>Angular 7 frontend, served at, say <a href="http://localhost:4200" rel="nofollow noreferrer">http://localhost:4200</a></li>
  <li>Express backend, served at, say <a href="http://localhost:3500" rel="nofollow noreferrer">http://localhost:3500</a></li>
  <li>Passport library for OAuth2 Authentication</li>
  </ol>
  
  <p>I am setting up OAuth2 flow from the serverside (Express / Node.js).
  On clicking the Login button from the frontend, request is sent to the server, 
  which gets redirected to Google to ask for user credentials / permissions etc.</p>
  
  <p>My callback URL is : <a href="http://localhost:3500/auth/callback" rel="nofollow noreferrer">http://localhost:3500/auth/callback</a>.</p>
  
  <p>Post successful login, what is a good way to redirect back to the Frontend URL i.e. <a href="http://localhost:4200/" rel="nofollow noreferrer">http://localhost:4200/</a> ?? Since the callback URL is on the serverside </p>