SafeCache policy has corner cases
According to Georg Koppen, SafeCache has some corner cases wrt some 3rd party content, especially content created from JavaScript. In particular, partners.eatsmarter.de is getting a unique cache id when sourced off of www.spiegel.de, instead of the id for www.spiegel.de.
There are also potential issues with our use of notificationCallbacks to obtain the sourcing domain. In some cases, we may also need to use the url from the loadGroup, but for www.spiegel.de this is not what is going wrong..