使用filePond，我如何在上传文件时将自定义数据(即galleryId (自定义))返回给客户端？

const pond = FilePond.create(inputElement, {
    server: {
        process: '/upload',
        revert: '/revert',
        headers: {
            'X-CSRF-TOKEN': 'your-csrf-token'
        },
        onload: (response) => {
            const galleryId = response.galleryId; // 从服务器返回的自定义数据
            // 处理返回的galleryId
        }
    }
});

const express = require('express');
const multer = require('multer');

const app = express();
const upload = multer({ dest: 'uploads/' });

app.post('/upload', upload.single('file'), (req, res) => {
    // 处理文件上传逻辑
    const file = req.file;
    const galleryId = req.body.galleryId; // 从请求中获取galleryId

    // 将galleryId与文件关联并保存到数据库或其他存储方式

    // 返回自定义数据给客户端
    res.json({ galleryId });
});

app.listen(3000, () => {
    console.log('Server is running on port 3000');
});