title: Enable Default Sound on FCM Push Notification for iOS
body: <p>I am trying to set the default sound for a push notification sent and have the following message object to pass through.</p>
  
  <pre><code>var message = {
        notification: {
          title: "X",
          body: "X",
          sound: 'default'
        }          
        token: fcmToken
   };
  </code></pre>
  
  <p>I continue, however, to receive the following error in my cloud function log: </p>
  
  <blockquote>
    <p>Error sending message: Error: Invalid JSON payload received. Unknown
    name "sound" at 'message.notification': Cannot find field.</p>
  </blockquote>
  
  <p>I've tried placing the sound property under the notification object, apns-payload-aps object, and cannot seem to locate documentation on the correct syntax to activate the default sound on iOS.</p>
  
  <p>Any help is appreciated.</p>