5.2.2.2. no-cache(response)
不带值
The "no-cache" response directive indicates that the response MUST
NOT be used to satisfy a subsequent request without successful
validation on the origin server. This allows an origin server to
prevent a cache from using it to satisfy a request without contacting
it, even by caches that have been configured to send stale responses.
request(no-cache)-response不能(MUST NOT)用来reuse，除非对其进行验证之后。例如:
Cache-Control: no-cache
带值
If the no-cache response directive specifies one or more field-names,
then a cache MAY use the response to satisfy a subsequent request,
subject to any other restrictions on caching. However, any header
fields in the response that have the field-name(s) listed MUST NOT be
sent in the response to a subsequent request without successful
revalidation with the origin server.
我怎么感觉这句话是这个意思，假设此时cache中有缓存：
request(no-cache:"X-User-Points")-response
根据rfc定义:
- cache可以reuse除了“X-User-Points” header以外的部分，将其发给client;或者
- cache可以为缓存发起条件验证，验证以后将最新的request(no-cache:"X-User-Points")-response返回给client；注意，如果验证了以后，
- 就不用排除“X-User-Points” header了
