First, you need to get two things
1) FIREBASE_SERVER_API_KEY
2) FIREBASE_NOTIFICATION_URL .
After that just pass them in the headers
{"Authorization" => "key=#{FIREBASE_SERVER_API_KEY}", "Content-Type" => "application/json"}
And in the body these
{"registration_ids": ["pass-device-token"], "priority":"high", "data":{}}
I also created a tutorial on how to integrate Firebase with ruby ββon rails.
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