apollo-biz/src/main/java/com/ctrip/framework/apollo/biz/service/AppNamespaceService.java/AppNamespaceService/isAppNamespaceNameUnique
class AppNamespaceService:  public boolean isAppNamespaceNameUnique(String appId, String namespaceName) {
    Objects.requireNonNull(appId, "AppId must not be null");
    Objects.requireNonNull(namespaceName, "Namespace must not be null");
    return Objects.isNull(appNamespaceRepository.findByAppIdAndName(appId, namespaceName));
  }