code: private CreateRouteResponseType createRoute(final String destinationCidrBlock,
              final String internetGatewayId, final String routeTableId) {
          CreateRouteResponseType ret = new CreateRouteResponseType();
          ret.setRequestId(UUID.randomUUID().toString());
          mockRouteTableController.createRoute(destinationCidrBlock, internetGatewayId, routeTableId);
  
          return ret;
      }
docs: Handles "createRoute" request to create route and returns response with a route table.
  @param destinationCidrBlock : Route destinationCidrBlock.
  @param internetGatewayId : for gateway Id.
  @param routeTableId : for Route.
  @return a CreateRouteResponseType with our new route.