RFC 7234: Prefer value from Cache-Control: s-maxage

[da2x]

This plugin’s cache is a shared cache. It should prefer the value specified in the s-maxage (shared cache= value over the max-age (client cache), and only use the max-age as a fallback if s-maxage isn’t present.

Example (should cache for 60 seconds):

Cache-Control: max-age=900, s-maxage: 60

https://tools.ietf.org/html/rfc7234#section-4.2.1

[nicolasazrak]

This should be implemented by https://github.com/pquerna/cachecontrol which is the library caddy-cache uses to parse headers. Can you create an issue in that repo?