A library to subscribe to GCM/FCM and receive notifications.
This library was developed inspired by push-receiver (https://github.com/MatthieuLemoine/push-receiver/).
MIT License
proto file is licensed by is The Chromium Authors. (BSD-style lisense) (copied it from https://chromium.googlesource.com/chromium/chromium/+/trunk/google_apis/gcm/protocol/)