docs: function routeSolver(routeItem, handler, resolver) {
      switch (typeof handler) {
      case 'function':
          // solve as function handler
          registerHandler(routeItem, null, routeItem.handler);
          break;
      case 'string':
          // solve as controller - action handler
          resolver(routeItem, handler);
          break;
      default:
          throw new Error('unknow route type');
      }
  }