Refactor default locale prefix to support clone() (#35874)

## Bug
fixes #35273

- [x] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`


## Documentation / Examples

- [ ] Make sure the linting passes by running `yarn lint`

docs/advanced-features/i18n-routing.md

@@ -170,24 +170,19 @@ import { NextRequest, NextResponse } from 'next/server'
 
 const PUBLIC_FILE = /\.(.*)$/
 
-const stripDefaultLocale = (str: string): string => {
-  const stripped = str.replace('/default', '')
-  return stripped
-}
-
 export function middleware(request: NextRequest) {
   const shouldHandleLocale =
     !PUBLIC_FILE.test(request.nextUrl.pathname) &&
     !request.nextUrl.pathname.includes('/api/') &&
     request.nextUrl.locale === 'default'
 
-  return shouldHandleLocale
-    ? NextResponse.redirect(
-        `/en${stripDefaultLocale(request.nextUrl.pathname)}${
-          request.nextUrl.search
-        }`
-      )
-    : undefined
+  if (shouldHandleLocale) {
+    const url = request.nextUrl.clone()
+    url.pathname = `/en${request.nextUrl.pathname}`
+    return NextResponse.redirect(url)
+  }
+
+  return undefined
 }
 ```