@Override
                    public @Nullable String load(@NonNull final String server) {
                        try {
                            Optional<?> login = RegisterUtils.doLogin(username, password, server.concat(Constants.LOGIN_PATH));
                            return login.map(String::valueOf).orElse(null);
                        } catch (Exception e) {
                            LOGGER.error("Login admin url :{} is fail, will retry. cause: {} ", server, e.getMessage());
                            return null;
                        }
                    }
Instantiates a new Http client register repository.

@param config the config
shenyu-register-center/shenyu-register-client/shenyu-register-client-http/src/main/java/org/apache/shenyu/register/client/http/HttpClientRegisterRepository.java