def transfer_doi(doi, options={})
      return OpenStruct.new(body: { "errors" => [{ "title" => "JWT or Username or password missing" }] }) unless options[:jwt].present? || (options[:username].present? && options[:password].present?)

      api_url = options[:sandbox] ? 'https://api.test.datacite.org' : 'https://api.datacite.org'