Cache invalidation

_From @JunTaoLuo on Thursday, September 15, 2016 2:15:48 PM_

Currently we only set the absolute timeouts for cache entries. There is no mechanism to explicitly invalidate a cache entry before expiry. Also, how would applications/users interact with this feature?

Note that invalidation is required by the RFC for unsafe methods, e.g. a successful PUT should invalidate any previous cached resources at the same URI.

_Copied from original issue: aspnet/ResponseCaching#38_

Start by locating the ASP.NET Core response-caching implementation and its handling of absolute cache-entry timeouts. Trace how applications currently interact with cached resources, then review the RFC requirement that a successful PUT invalidate the previous resource at the same URI. Done means an agreed invalidation mechanism and application-facing behavior are implemented and covered by tests.

Written by the indexing model from the issue text.