Overrides HttpServletResponse.sendRedirect(String) and handles it by
setting the HTTP status and "Location" headers, which keeps the Servlet
container from re-writing relative redirect URLs into absolute ones.
Servlet containers are required to do that but against the recommendation of
RFC 7231 Section 7.1.2,
and furthermore not necessarily taking into account "X-Forwarded" headers.
Note: While relative redirects are recommended in the
RFC, under some configurations with reverse proxies they may not work.