newforms-admin: need mechanism for further modifying a newly saved object after it has been saved

[simon]

ModelAdmin.save_add(...) creates a new_object and then returns an HttpResponseRedirect(). It would be really useful if there was a hook for further modifying that object after it had been saved.

It's possible to do this using a custom save() method on the model at the moment, but that has two limitations:

1. The save() method doesn't have access to a request object. Admin customisations often involve extra form stuff being passed in as part of the request.
2. You might want custom behaviour that only runs on objects created using the admin, not objects created using other means.

Having a post_save_add() method that is passed the request and the newly created object and does nothing by default (but can be over-ridden in ModelAdmin subclasses) would be one way of solving this, but I'm not sure it's the best way.