register_and_post.swift

    func application( _ application: UIApplication, didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data) {
        let tokenParts = deviceToken.map { data in String(format: "%02.2hhx", data) }
        let token = tokenParts.joined()
        print("Device Token: \(token)")
        sendDeviceToken(device: Device(platform: "ios", deviceToken: token))
    }

    struct Device: Codable {
        var platform: String
        var deviceToken: String
    }
    func sendDeviceToken(device: Device) {
        var request = URLRequest(url: URL(string: "http://172.20.3.158:9090/devices")!)
        request.httpMethod = "POST"
        request.addValue("application/json", forHTTPHeaderField: "Content-Type")
        request.addValue("application/json", forHTTPHeaderField: "Accept")
        request.httpBody = try? JSONEncoder().encode(device)
        URLSession.shared.dataTask(with:request, completionHandler: {(data, response, error) in
            if error != nil {
                print(error)
            } else {
                print(data)
            }
        }).resume()
    }