Does anyone know why Firebase doesn't support notification delivery on iOS? This is supported by other messaging frameworks such as OneSignal by hooking into Notification Service Extensions.

Firebase does have a FIRMessagingExtensionHelper class which has an exportDeliveryMetricsToBigQuery method — however I didn't see references to this in the docs, how it should be used, or whether it suits my needs.

The ideal scenario is that Firebase can just report iOS delivery rates in the console. It's confusing to me why this is not made simple, and if anyone has some insight here it would be much appreciated.