docs: fix bug in ssr guide email flow pkce (#19281)

apps/docs/pages/guides/auth/server-side/email-based-auth-with-pkce-flow-for-ssr.mdx

@@ -31,13 +31,15 @@ Create a new file at `app/auth/confirm/route.ts` and populate with the following
 import { createServerClient, type CookieOptions } from '@supabase/ssr'
 import { type EmailOtpType } from '@supabase/supabase-js'
 import { cookies } from 'next/headers'
-import { NextResponse } from 'next/server'
+import { NextRequest, NextResponse } from 'next/server'
 
-export async function GET(request: Request) {
+export async function GET(request: NextRequest) {
   const { searchParams } = new URL(request.url)
   const token_hash = searchParams.get('token_hash')
   const type = searchParams.get('type') as EmailOtpType | null
   const next = searchParams.get('next') ?? '/'
+  const redirectTo = request.nextUrl.clone()
+  redirectTo.pathname = next
 
   if (token_hash && type) {
     const cookieStore = cookies()
@@ -64,12 +66,13 @@ export async function GET(request: Request) {
       token_hash,
     })
     if (!error) {
-      return NextResponse.redirect(next)
+      return NextResponse.redirect(redirectTo)
     }
   }
 
   // return the user to an error page with some instructions
-  return NextResponse.redirect('/auth/auth-code-error')
+  redirectTo.pathname = '/auth/auth-code-error'
+  return NextResponse.redirect(redirectTo)
 }
 ```