ios - GCMMessage with content-available flag

Question

I have set up Android and iOS clients with fcm and want to send GCMMessages from pinpoint. Standard push notifications are working fine on both Android and IOS, silent push notification is working for Android but it is not working for IOS.

{
  "GCMMessage": {
    "RawContent": "{\"data\":{\"key1\":\"test1\",\"key2\":\"test2\"},\"content-available\":1}"
  }
}

This is the sample GCMMessage payload that I am trying to send.