@Override
            public com.squareup.okhttp.Request authenticate(Proxy proxy, com.squareup.okhttp.Response response) throws IOException {
                boolean isDemo = ServerConfig.DEMO_HOST_NAME.equals(response.request().url().getHost());
                String user = isDemo ? ServerConfig.DEMO_USER_NAME : ServerConfig.STAGING_USER_NAME;
                String passw = isDemo ? ServerConfig.DEMO_PASSWORD : ServerConfig.STAGING_PASSWORD;
                String credential = Credentials.basic(user, passw);
                return response.request().newBuilder()
                        .header("Authorization", credential)
                        .build();
            }