Add Confirmation Dialog when Adding Duplicate Combo

[GordonsKitchen]

It would be good to have a confirmation dialog pop up when an editor tries to add a combo that is a duplicate of a pre-existing combo. I was thinking of something similar to the dialog that pops up when you delete a combo. A message like "The combo you are trying to add is a duplicate of combo [ID]. Would you still like to add this combo?" and then a yes/no answer. Yes adds the combo as normal, no takes you back to the "Add Combo" screen.

I think this would be good to have to ward out accidental duplicates before they are added and then (likely) need deleted. If we do need to have duplicates for some reason, we can still do so.

[ldeluigi]

Today I tried working on this request without exploiting third party software, and I concluded that it costs too much dev efforts and time to get it done well. Django, the framework powering the backend, doesn't allow easy customization to implement a confirmation page that conditionally pops out based on related objects such as cards, templates and features in a combo, which need to be inspected in order to detect any duplicate.