# File lib/openid/consumer.rb, line 772
    def redirect_url(trust_root, return_to, immediate=false)
      # add the nonce into the return_to url
      return_to = OpenID::Util.append_args(return_to, @return_to_args)

      redir_args = {
        "openid.identity" => @server_id,
        "openid.return_to" => return_to,
        "openid.trust_root" => trust_root,
        "openid.mode" => immediate ? 'checkid_immediate' : 'checkid_setup'
      }

      redir_args["openid.assoc_handle"] = @assoc.handle if @assoc
      redir_args.update(@extra_args)
     
      return OpenID::Util.append_args(server_url, redir_args).to_s
    end