Adding cookie "Partitioned" flag

**Is your feature request related to a problem? Please describe.**

Recently, browsers have added a new flag called `Partitioned` that allow cross-origin cookie setting on browsers where third party cookies are disabled (Safari, Firefox, future Chrome):

https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Set-Cookie#partitioned

https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Set-Cookie#partitioned_cookie

https://developer.mozilla.org/en-US/docs/Web/Privacy/Privacy_sandbox/Partitioned_cookies

**Describe the solution you'd like**

I'd love for the currently available Cookie class to support the new `Partitioned` flag.

**Describe alternatives you've considered**

It does not seem to be currently possible to set arbitrary strings as flags on Drogon cookies.