perfect, but how do i know if ctx.request.body is a file and get the file name?

let photo = document.getElementById("image-file").files[0];
let formData = new FormData();
     
formData.append("photo", photo);
fetch('/upload/image', {method: "POST", body: formData});

let photo = document.getElementById("image-file").files[0];
let formData = new FormData();
     
formData.append("photo", photo);
fetch('/upload/image', {method: "POST", body: formData});

Your worker has access to the following bindings:
- D1 Databases:
  - DB: database-name (database-id)
⎔ Starting local server...

Your worker has access to the following bindings:
- D1 Databases:
  - DB: database-name (database-id)
⎔ Starting local server...

{
  "version": "1",
  "include": ["/*"],
  "exclude": "/"
}

{
  "version": "1",
  "include": ["/*"],
  "exclude": "/"
}

// src/middleware.js
export async function onRequest({ request, locals }, next) {
    // Check if the current request path matches the specific form action path
    if (new URL(request.url).pathname === '/form-path' && request.method === 'POST') {
        try {
            // Process form data
            const formData = await request.formData();

            // Example of form data processing.
            if(formData.get('name') !== "john") {
                throw new Error("Name must be john!")
            }

            // After processing successfully, redirect to `/form-submitted`
            return Response.redirect(new URL("/form-submitted", request.url), 302);
        } catch (error) {
            // If there's an error in processing, set `locals.formError`
            // This can later be checked in the endpoint handling the form submission
            locals.formError = error.message;
        }
    }

    // If the path does not match, proceed with the normal request flow.
    return next();
}

// src/middleware.js
export async function onRequest({ request, locals }, next) {
    // Check if the current request path matches the specific form action path
    if (new URL(request.url).pathname === '/form-path' && request.method === 'POST') {
        try {
            // Process form data
            const formData = await request.formData();

            // Example of form data processing.
            if(formData.get('name') !== "john") {
                throw new Error("Name must be john!")
            }

            // After processing successfully, redirect to `/form-submitted`
            return Response.redirect(new URL("/form-submitted", request.url), 302);
        } catch (error) {
            // If there's an error in processing, set `locals.formError`
            // This can later be checked in the endpoint handling the form submission
            locals.formError = error.message;
        }
    }

    // If the path does not match, proceed with the normal request flow.
    return next();
}