I could make Contact Form by using Gatsby Functions and SendGrid. The value of Input text and Textarea can be successfully sent, but I am wondering how I can handle the file to upload and send. <input type="file" id="formFile" /> In the case of Next.js' API Router, it seems to be possible by installing "Next-connect" and "multiparty" package. Any idea in the case of Gatsby Functions?

api/form_sent.js

export default function formHandler(req, res) {
        const sgMail = require('@sendgrid/mail');
        sgMail.setApiKey(process.env.SENDGRID_APIKEY);

        const { method, body } = req;

        const mailData = {
          from: process.env.AUTHORIZED_SENDER,
          to: body.formEmail,
          subject: 'question from web',
          html: `<p>${body.formName}<p>${body.formTextarea}</p>`,
        }

        const results = sgMail.send(mailData)
          .then(result => res.status(200).json(JSON.stringify(result)))
          .catch(error => res.status(500).json(JSON.stringify(error)))

}

pages/form.js

import * as React from "react"
import Layout from "../components/layout"

export default function FormPage() {
    const [serverResponse, setServerResponse] = React.useState(``)

    async function onSubmit(e) {
        e.preventDefault()
        const response = await window
        .fetch(`/api/send`, {
            method: `POST`,
            headers: {
            "content-type": "application/json",
            },
            body: JSON.stringify(value),
        })
        .then(res => res.json())
        setServerResponse(response)
    }

    return (
        <Layout>
                    <form onSubmit={onSubmit} method="POST" action="/api/send">
                            <input type="text" id="formName" />
                            <input type="email" id="formEmail" />
                            <textarea id="formTextarea"></textarea>
                            <input type="file" id="formFile" />
                            <button type="submit">Send</button>
                    </form>
        </Layout>