誰能解釋我如何在 Laravel 中使用托管字段進行有效的 Braintree 付款。我試圖自己查看文檔，但無法使其正常工作。我在控制器中創建了要發送到視圖的令牌，例如：$gateway = new \Braintree\Gateway([            'environment' => config('services.braintree.environment'),            'merchantId' => config('services.braintree.merchantId'),            'publicKey' => config('services.braintree.publicKey'),            'privateKey' => config('services.braintree.privateKey')        ]);$paypalToken = $gateway->ClientToken()->generate();return view('checkout')->with(['paypalToken' => $paypalToken]);這是我處理付款的方法：        $gateway = new \Braintree\Gateway([            'environment' => config('services.braintree.environment'),            'merchantId' => config('services.braintree.merchantId'),            'publicKey' => config('services.braintree.publicKey'),            'privateKey' => config('services.braintree.privateKey')        ]);        $nonce = $request->payment_method_nonce;        $result = $gateway->transaction()->sale([            'amount' => round(getNumbers()->get('newTotal') / 100, 2),            'paymentMethodNonce' => $nonce,            'options' => [              'submitForSettlement' => True            ]          ]);        if ($result->success) {            $transaction = $result->transaction;            $order = $this->addToOrdersTablesPaypal(                $email,                $firstName.' '.$lastName,                null            );            return redirect()->route('confirmation.index')->with('success_message', 'Thank you! Your payment has been successfully accepted!');        } else {            $order = $this->addToOrdersTablesPaypal(                $email,                $firstName.' '.$firstName,                $result->message            );            return back()->withErrors('An error occurred with the message: '.$result->message);        }誰能幫助我，了解缺少什么？