RFC-2616: cache control support
| JSON representation | 
|---|
| { "directive": string, "age": string, "expires": string } | 
| Fields | |
|---|---|
| directive | 
 14.9 request and response directives | 
| age | 
 14.6 response cache age, in seconds since the response is generated | 
| expires | 
 14.21 response cache expires, in RFC 1123 date format |