We want to create a tutorial to explain it but let's see if I can
guide you a bit...
You don't need to configure the apple push certificate in liferay,
you will only need to configure the firebase api key with the liferay
push portlet. It comes preinstalled in 7.1. The configuration is in
system settings, notifications (if you search for firebase it's easier).
The hardest part is to get the token and register the device in
liferay/apple. To get the token you have to read apple documentation.
I recommend you to generate a token and test it manually first
(registering it in liferay, platform firebase) and adding the code to
show the notification.
To register it programatically, basically you have to call this code but
instead of using apple as the platform, use firebase. Specifically
the registerDeviceTokenData function.
