apollo-portal/src/main/java/com/ctrip/framework/apollo/portal/util/ConfigFileUtils.java/ConfigFileUtils/genNamespacePath
class ConfigFileUtils:  public static String genNamespacePath(
      final String ownerName,
      final String appId,
      final Env env,
      final String configFilename
  ) {
    return String.join(File.separator, ownerName, appId, env.getName(), configFilename);
  }