Marks the response as personalized with the given variant identifier. Commerce Cloud Digital identifies unique
pages based on a combination of pricebook, promotion, sorting rule and A/B test segments, caches the different
variants of the page, and then delivers the correct version to the user. If a page is personalized by means other
than pricebook, promotion, sorting rule and A/B test, the page must not be cached, because the wrong variants of
the page would be delivered to the user. For performance reasons, a page should only be marked as personalized if
it really is. Otherwise, the performance can unnecessarily degrade.
This method has the same effect as using <iscache varyby="price_promotion" /> tag in an ISML template. Once
the vary-by value was set, either using this method or by the <iscache> tag in a template, the entire
response is treated as personalized.
the variation criteria, currently only "price_promotion" is supported, any other value has no effect