In case of successful unsafe method on a stored resource, the cached entry
must be invalidated (see RFC7234#4.4).
A "non-error response" is one with a 2xx (Successful) or 3xx (Redirection)
status code.
This implies that the primary hash must now be calculated on requests
that have an unsafe method (POST or PUT for instance) so that we can
disable the corresponding entries when we process the response.
