docs: private TreeBuilder<ResourceMeta> baseStorage(TreeBuilder<ResourceMeta> builder) {
          //set base using file storage, could be overridden
          Map<String, String> config1 = expandConfig(getBaseStorageConfig());
          logger.debug("Default base storage provider: " + getBaseStorageType() + ", " +
                       "config: " + config1);
  
          StoragePlugin base = loadPlugin(
                  getBaseStorageType(),
                  config1,
                  storagePluginProviderService
          );
          if(null==base) {
              throw new IllegalArgumentException("Plugin could not be loaded: " + getBaseStorageType());
          }
          return builder.base(base);
      }