def save(file_path)
      save_path = File.join(remote_storage_prefix, File.basename(file_path))
      @store.save(file_path, save_path)
    end
def save(file_path)
      save_path = File.join(remote_storage_prefix, File.basename(file_path))
      @store.save(file_path, save_path)
    end
Takes a local filesystem path, saves the file to S3, and returns the
 public (or authenticated) url on S3 where the file can be accessed.