How to get a server key and a sender ID for WebPush
1. Access to https://console.firebase.google.com
2. Push [Add project] for creating the project
3. Click the settin icon to open [Project settings]
4. Select [CLOUD MESSAGING]
5. Find the “Server key” and the “Sender ID”
6. Go to Brekeke SIP Server’a [Push Notification]->[Application] page
7. Push [New WebPush Application]
8. Enter Sender ID at [Application ID]
9. Enter the Server key at [Server Key]