OutputCaching: Support for x-vs-store-code

[benjick]

Short Description and Why It's Useful

Currently it's not possible to use the x-vs-store-code header and outputCaching because the caching only looks at req.url. This fixes that.

Which Environment This Relates To

Check your case. In case of any doubts please read about Release Cycle

• Test version (https://test.storefrontcloud.io) - this is a new feature or improvement for Vue Storefront. I've created branch from develop branch and want to merge it back to develop
• RC version (https://next.storefrontcloud.io) - this is a stabilisation fix for Release Candidate of Vue Storefront. I've created branch from release branch and want to merge it back to release
• Stable version (https://demo.storefrontcloud.io) - this is an important fix for current stable version. I've created branch from hotfix or master branch and want to merge it back to hotfix

Upgrade Notes and Changelog

• No upgrade steps required (100% backward compatibility and no breaking changes)
• I've updated the Upgrade notes and Changelog on how to port existing Vue Storefront sites with this new feature

IMPORTANT NOTICE - Remember to update CHANGELOG.md with description of your change

Contribution and Currently Important Rules Acceptance

• I read and followed contribution rules

[benjick]

Not sure what changelog to put it in

[andrzejewsky]

@benjick just put Added OutputCaching: Support for x-vs-store-code - @benjick (#3979) 😃

[benjick]

Thanks, didn't see the "[1.12.0-rc1] - UNRELEASED" at first, was probably looking in the wrong branch! 👍