title: Getting app store / google play customer ID for customer support IAP Unity
body: <p>We configured an "Email support" button- when the user sends all kind of logs to us,
  but we also need to identify the user ID in the Apple Store or Google Play and add it to the same email
  so we can compare the status of purchase with the stores,
  but how can we make sure it's the same user?</p>
  
  <p>How do we get the unique ID the user has on Apple Store or Google Play in code? (in app purchase Unity)</p>