private void handleEmptyRequestAndRedirect(final RoutingContext routingContext) {
    final HttpServerResponse response = routingContext.response();
    if (response.closed()) {
      return;
    }
    response.setStatusCode(HttpResponseStatus.PERMANENT_REDIRECT.code());
    response.putHeader("Location", "/graphql");
    response.end();
  }
Returns the URL of the GraphQL HTTP service.

<p>This method constructs and returns the URL that the HTTP server is bound to. If the server
is not running, it returns an empty string.

@return the URL of the HTTP server, or an empty string if the server is not running.
ethereum/api/src/main/java/org/hyperledger/besu/ethereum/api/graphql/GraphQLHttpService.java