docs: public Path normalizeOutputPath(FileResource resource) {
      
      Path resourcePath = resource.getPath();
  
      Path rel = Optional.ofNullable((contentDir.relativize(resourcePath)).getParent())//
          .orElseGet(() -> resourcePath.getFileSystem().getPath(""));
  
      String finalOutput = rel.resolve(finalOutputName(resource)).toString();
  
      // outputDir and contentDir can have different underlying FileSystems
      return outputDir.resolve(finalOutput);
    }