There's a big consequence to this for compatible with RFC 2965 Cookies. In particular,
this drops our ability to support 'Set-Cookie2' headers, and some features used there
including quoted attributes like 'Max-Age="25"'. This is the right move for interop with
browsers, and likely to make things better for application developers, but some
people who strictly followed the RFC 2965 spec will be broken. (That spec was never
seriously adopted anywhere, which is the entire motivation of RFC 6265.)
The upside is the CookieJar interface is now much more straightforward. This is
particularly good going forward, and for clients who don't have to worry about the
strangeness of things like $Version=1 in the RFC 2965 spec.