A Boolean value that indicates whether to restrict the cookie to requests sent back to the same site that created it.
- iOS 13.0+
- macOS 10.15+
- Mac Catalyst 13.0+
- tvOS 13.0+
- watchOS 6.0+
Along with the policy values defined by
HTTPCookie, this property may also be
nil. In this case, cross-site requests include the cookie.