Google independent notification messaging (do not rely on FCM)

[anton-isidore]

With implementation of the BOLT12 it became very important to be online to receive payments.

On GrapheneOS we got this notification warning us:

Instead of relying on Google servers it would be great to have own way of delivering notification in case Google Play Services are not present on the phone.

Market standard seems to be running a foreground service. This is what Signal, Telegram, Element, ... and many other apps are doing.

There is also UnifiedPush but I am not sure if it is usable in this context (there is already issue for it here: #554)

Sources:

• https://github.com/Telegram-FOSS-Team/Telegram-FOSS/blob/master/Notifications.md
• https://developer.android.com/develop/background-work/services/foreground-services

[MasterixCZ]

It would be nice if Phoenix was more FOSS and friendly to deGoogled operating systems

[xronin01]

add support for UnifiedPush 🙏🙏🙏

[dpad85]

The warning message about FCM could let the user choose to run the app as a permanent foreground service. It should not be too hard to do since we are already using a foreground service to run the app in the background. UnifiedPush however would need much more work.