ref
https://linear.app/tryghost/issue/KTLO-58/dont-send-ghost-acess-cookies-if-no-member-is-logged-in
- Currently when member's caching is enabled, but no member is logged
in, we always send `ghost-access=null;` and `ghost-access-hmac=null;`
cookies in the requests to `/members/api/member/`. This is done to clear
the cookies, but an unintended consequence is that these requests can
never be cached since there is a cookie in the response.
- This PR removes the cookies from the requests when no member is logged
in, the cookies will not be sent, allowing the requests to be cached
- It also unsets the cookies when deleting a member's session, so that
the cookies are not sent in the requests after the member logs out
- This should improve the cache hit ratio with members caching enabled
4a6d427673