Extend release notes with jQuery upgrade
[Backport] Fix bug with product class lookups in variants

This causes availability messages to fail in templates as an exception
is raised for variant products which don't define a product class.

Cherry-pick of 72eaafecb356032d198248e485a0fbcdfad5e3f2 back onto
releases branch.
[Backport] Handle group products in stockrecord template partial

Before this, group products were always shown as unavailable as they
didn't have a stockrecord - even though their variant products did.

Cherry-pick of f2922c9b3a63f035e20efae99a9fd3ba2e5c3b6d.
[Backport] Correct product URL on thank-you page

Cherry-pick of af6edf88ea419a4dc2e409ea61686f645c3ec19c