Bad request handler.

[tomas-langer]

Resolves #1893

Signed-off-by: Tomas Langer tomas.langer@oracle.com

To customize bad request handling:

 webServer = WebServer.builder()
                .directHandler(MyClass::directHandler, EventType.BAD_REQUEST)
                .routing(routing())
                .build();

and the handler:

private static TransportResponse badRequestHandler(DirectHandler.TransportRequest request,
                                                       DirectHandler.EventType eventType,
                                                       Http.ResponseStatus defaultStatus,
                                                       String message) {
              return TransportResponse.builder()
                    .status(Http.Status.TEMPORARY_REDIRECT_307)
                    .header(Http.Header.LOCATION, "/errorPage")
                    .build();
}