Thinking about this some more, I think to replace model.Package with an interface. The existing struct of that name will become JsonPackage that implements it.

Thinking about this some more, I think to replace model.Package with an interface. The existing struct of that name will become JsonPackage that implements it. This is because the CKAN representation of a dataset has some modelling problems (that are being addressed in parallel by the CKAN team) and it isn't clear that the existing models as represented in the JSON should overly inform the functioning of the ckand aggregator.