title: Passport-js How to create a custom strategy
body: <p>I am looking to create my own strategy.</p>
  
  <p>I have <code>client_id</code>, <code>client_secret</code> and related meta data. I also know the flow of execution. So I want to create my own strategy and add my custom logic for authentication.</p>
  
  <p>I looked at <a href="https://www.npmjs.com/package/passport-strategy" rel="noreferrer">passport-strategy</a>, but I am not understanding how to implement my own strategy. Can anyone explain it?</p>