Prior to this commit, the `ContentCachingRequestWrapper` class would
cache the response content only if the reponse would be consumed using
its InputStream. In case of a Form request, Spring MVC consumes the
response using the `getParameter*` Servlet API methods. This causes the
cached content to never be written.
This commit makes the `ContentCachingResponseWrapper` write the request
body to the cache buffer by using the `getParameter*` API, thus avoiding
those issues.
Issue: SPR-7913
cf86ecddb5