Add a test to verify that the ForwardedHeaderFilter contextPath override preserves URL encoding
as it should.

Issue SPR-15422

Previously ForwardedHeaderFilter would override the requestURI with a URL decoded value. This would cause
problems when using a URL encoded requestURI since downstream Filters would not see the URL encoded
value as they should.

This commit resolves this issue by ensuring that the requestURI is properly encoded.

Issues SPR-15422

This commit makes CodecException handling consistent between functional
and annotation-based APIs. It now returns by default 4xx status code
for decoding error and 5xx for encoding error + print the error reason
in logs without the full stack trace in both variants.

Issue: SPR-15355

Issue: SPR-14923

Generic type resolution algorithm in GenericTypeResolver shared between Jackson and Gson.

Issue: SPR-15381

Issue: SPR-15426

* pr/1383:
  Fix typo

Closes gh-1383

* pr/1382:
  Update copyright header
  Fix typo in AfterReturningAdviceInterceptor JavaDoc

Closes gh-1382

See gh-1382

Issue: SPR-15227

Issue: SPR-15418

The java.util.Optional wrapper should not affect the support for
"request param" arguments with or without the annotation as it
works on the Spring MVC side.

Issue: SPR-15211

Previously ForwardedHeaderFilter would return the same StringBuffer for every invocation. This
meant that users that modified the StringBuffer changed the state of the HttpServletRequest.

This commit ensures that a new StringBuffer is always returned for ForwardedHeaderFilter.

Issue: SPR-15423

Issue: SPR-15417

Issue: SPR-14512

Issue: SPR-15409

This commit uses the newly introduced
`PathPattern.getPathRemaining(String)` in the functional web framework.
With this change, all path predicates can be used for nested router
functions, so the `pathPrefix` predicate is no longer required and has
been removed.

Issue: SPR-15336

With this change there is a new getPathRemaining() method on
PathPattern objects. It is called with a path and returns
the path remaining once the path pattern in question has
matched as much as it can of that path. For example if the
pattern is /fo* and the path is /foo/bar then getPathRemaining
will return /bar. This allows for a set of pathpatterns
to work together in sequence to match a complete entire path.

Issue: SPR-15336

This commit deletes images that are no longer used in the Reference
Manual.

Issue: SPR-14997

This commit uses a tip provided by @mojavelinux to set the syntax
highlighter to Rouge for the PDF version of the User Guide.

Once Asciidoctor 1.5.7 has been released we will likely switch to Rouge
for the HTML version of the Reference Manual as well.

Issue: SPR-14997

Issue: SPR-14512

Issue: SPR-15411

Issue: SPR-15411