def image_directory
      @image_directory ||= begin
        date_dir = Time.zone.now.strftime('%Y/%m')
        File.join(IMAGE_DIRECTORY, date_dir)
      end
    end
def image_directory
      @image_directory ||= begin
        date_dir = Time.zone.now.strftime('%Y/%m')
        File.join(IMAGE_DIRECTORY, date_dir)
      end
    end
Image directory with year/month subdirectories.

 @return [String]