class Authentication: AuthenticationProtocol {

    func authenticateUser(with username: String, password: String, completion: @escaping (_ user: UserModel?, _ error: Error?) -> Void) -> Cancellable {

        let url = URL(string: "authenticate", relativeTo: APIConstants.baseURL)!
        let parameters: [String: Any] = [ "username": username, "password": password]
        let request = URLRequest.createRequest(method: .post, url: url, parameters: parameters)

        let task = urlSession.dataTask(with: request) { [weak self] (data, response, error) in
            self?.handleResponse(data: data, response: response, error: error, completion: completion)
        }
        task.resume()

        return task
    }
}