def show_headers
      mail = with_email_locale { mail_and_body.first }
      render partial: 'rails_email_preview/emails/headers', locals: {mail: mail}
    end
def show_headers
      mail = with_email_locale { mail_and_body.first }
      render partial: 'rails_email_preview/emails/headers', locals: {mail: mail}
    end
Render headers partial. Used by the CMS integration to refetch headers after editing.