accept all cookies set by the main document loaded in the application using libsoup.
An example of the most common case, web browsers, would be: If http://www.example.com is the page loaded, accept all cookies set by example.com, but if a resource from http://www.third-party.com is loaded from that page reject any cookie that it could try to set. For libsoup to be able to tell apart first party cookies from the rest, the application must call [[email protected]_first_party] on each outgoing [class@Message], setting the [[email protected]] of the main document. If no first party is set in a message when this policy is in effect, cookies will be assumed to be third party by default.