public static String toFilename(
      final String appId,
      final String clusterName,
      final String namespace,
      final ConfigFileFormat configFileFormat
  ) {
    final String suffix;
    if (ConfigFileFormat.Properties.equals(configFileFormat)) {
      suffix = "." + ConfigFileFormat.Properties.getValue();
    } else {
      suffix = "";
    }
    return appId + "+" + clusterName + "+" + namespace + suffix;
  }
@Test
  public void toFilename() {
    final String propertiesFilename0 = ConfigFileUtils.toFilename("123", "default", "application", ConfigFileFormat.Properties);
    logger.info("propertiesFilename0 {}", propertiesFilename0);
    assertEquals("123+default+application.properties", propertiesFilename0);

    final String ymlFilename0 = ConfigFileUtils.toFilename("666", "none", "cc.yml", ConfigFileFormat.YML);
    logger.info("ymlFilename0 {}", ymlFilename0);
    assertEquals("666+none+cc.yml", ymlFilename0);
  }