3.x changes to use FOS HttpCache's header for user context hash, which is good as we then drop something which was different from upstream (due to us introducing this first before contributing it to FOS.. anyway).

This breaks any previous eZ user land code using this:

$response->setVary('X-User-Hash');

Such code will currently have to be changed to:

$response->setVary('X-User-Context-Hash');

It might be a good idea to introduce an abstraction for this on ezplatform-http-cache 0.9 and up, so people can prepare for this change.

Alternative is to contribute some sort of abstraction for this in FOSHttpCache, but then it will be 3.x only.