Partitioned cookies on Python <3.14

[Dreamsorcerer]

In aiohttp 3.12 we'll have support for partitioned cookies, but this is dependent on upstream support in Python 3.14+.

If anyone needs support in an older release of Python, it can be monkey patched with this code:

if sys.version_info < (3, 14):
    from http import cookies

    # See: https://github.com/python/cpython/issues/112713
    cookies.Morsel._reserved["partitioned"] = "partitioned" 
    cookies.Morsel._flags.add("partitioned")

I'll leave this as a pinned issue for a couple of years until the feature is more widely available without monkey patching.