Currently, AbstractTermPropertyLabelResolver passes a key (concatenated in WikibaseClient::getPropertyLabelResolver()) directly into BagOStuff methods, without using any make*Key() method. This is bad; if we want the cache key to be shared between wikis (and it looks like we do), then we should explicitly use makeGlobalKey(), otherwise makeKey().

See also T255116 for the investigation that led to the creation of this task.