title: How to generate promo code for android app subscription?
body: <p>I want to generate promo code for my app subscription, but when i 
           go to promotion on google play console and trying to add/GET, it 
           just give a message </p>
  
  <blockquote>
    <p>This product is not available for promotion.</p>
  </blockquote>
  
  <p>Please help me if any one have any solution.</p>