title: "Error : Use of undeclared type MessagingDelegate" in Firebase messaging
body: <p>I have updated my firebase messaging pod recently and followed the Quickstart guide of Firebase to perform necessary changes of upgradation. </p>
  
  <p>I added the new <code>extension AppDelegate : MessagingDelegate</code> extension but getting certain errors. </p>
  
  <p><a href="https://i.stack.imgur.com/yPNBn.png" rel="noreferrer"><img src="https://i.stack.imgur.com/yPNBn.png" alt="enter image description here"></a></p>