* [FIX] Set properly attribute ``content-available`` for APNS payload. The attribute indicates that push notification should be considered [background](https://developer.apple.com/documentation/usernotifications/setting_up_a_remote_notification_server/pushing_background_updates_to_your_app).
1.3.3
Not secure
* [FIX] Use numeric representation for boolean attributes ``mutable-content`` and ``content-available``.
1.3.2
Not secure
* [FIX] Encode ``Aps`` message according to APNS [specification](https://developer.apple.com/documentation/usernotifications/setting_up_a_remote_notification_server/generating_a_remote_notification) * [FIX] Util ``cleanup_firebase_message`` to remove null values for dict object. * [CHORE] Update dependencies
1.3.1
Not secure
* [FIX] ``APNSPayload`` message no longer support attribute ``custom_data``
1.3.0
Not secure
* [FIX] APNS custom data properly incorporate into the push notification payload. So instead of passing ``custom_data`` as-is into payload and by that introducing one more nested level, extract all the key from ``custom_data`` and put them on the same level as ``aps`` attribute.