Cairngorm doesn't prevent you from adding an addition package
to it's underlying structure. This particular logic feels like a
common utility method that could be used by the business, model, or
view layers. As such, I would make a new sibling package called
common that would house this utility. If you wanted to, you could
also make your own SWC containing this type of basic functionality
and import it from any of the Cairngorm layers as needed.