The NextRequest (body is read via req.json()).
Same InitRoutesOptions passed to getEmailAuthRoutes; used for onError when validation fails.
Promise of either { error: NextResponse } (validation failed) or { data: { password, ...rest } } with the validated payload.
Parses and validates the JSON body for sign-up/login routes: ensures
passwordis present and, ifTURNSTILE_KEYis set, validates the Cloudflare Turnstile captcha.