code: public function handle(Request $request, Closure $next)
      {
          if (Config::get('shopify-app.billing_enabled') === true) {
              $shop = ShopifyApp::shop();
              if (!$shop->isFreemium() && !$shop->isGrandfathered() && !$shop->plan) {
                  // They're not grandfathered in, and there is no charge or charge was declined... redirect to billing
                  return Redirect::route('billing');
              }
          }
  
          // Move on, everything's fine
          return $next($request);
      }
docs: Checks if a shop has paid for access.
  
  @param \Illuminate\Http\Request $request
  @param \Closure                 $next
  
  @return mixed