Trigger background message handler with data in payload

[leolux]

Regarding the documentation, the method "setBackgroundMessageHandler" of the service worker should be triggered when the payload contains data, not if the notification contains data:

messaging.setBackgroundMessageHandler(...)

How to send a web push message using firebase-admin-java that contains data in the payload that triggers this callback method?

[google-oss-bot]

I couldn't figure out how to label this issue, so I've labeled it for a human to triage. Hang tight.