Push service

[Huber1]

Clients need to register for push events. This allows the Backend to send Push-Messages to devices.

Endpoints needed:

POST /device: Register device for push service
example request:

{
  "deviceId": "string",
  "publicKey": "string",
  "deviceType": "IOS"
}

DELETE /device{deviceId}: Remove device from push service

The devices must be persisted on-disk.
Later, messages can be sent to the saved ids