Provide FCM integration

[pontello]

This API is currently only available for the Admin Node.js SDK.

It would be great having it here as well. Is it somehow on the roadmap?

https://firebase.google.com/docs/cloud-messaging/admin/

[google-oss-bot]

Hey there! I couldn't figure out what this issue is about, so I've labeled it for a human to triage. Hang tight.

[google-oss-bot]

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[hiranya911]

@nilsonpontello Definitely on the roadmap. No specific release date yet, but it's coming soon.

[hiranya911]

This was released today: https://firebase.google.com/support/release-notes/admin/java#5.9.0