This class determines whether a cache can serve a stored response from request. It
is "Constructing Responses from Caches" section in RFC 7234.
If there are multiple matches, the most recent response must be sent for
evaluation, as determined by the Date header field.
Returns a ServeFresh if the cached response is fresh enough.
Clients can send the max-age or min-fresh cache directives in a
request to constrain or relax freshness calculations for the
corresponding response (Section 5.2.1).
Determines if a stale response without validation is appropriate.