code: public function handle(Request $request, Closure $next)
      {
          $hmac = $request->header('x-shopify-hmac-sha256') ?: '';
          $shop = $request->header('x-shopify-shop-domain');
          $data = $request->getContent();
  
          $hmacLocal = ShopifyApp::createHmac(['data' => $data, 'raw' => true, 'encode' => true]);
          if (!hash_equals($hmac, $hmacLocal) || empty($shop)) {
              // Issue with HMAC or missing shop header
              return Response::make('Invalid webhook signature.', 401);
          }
  
          // All good, process webhook
          return $next($request);
      }
docs: Handle an incoming request to ensure webhook is valid.
  
  @param \Illuminate\Http\Request $request
  @param \Closure                 $next
  
  @return mixed