Force Generator Combos to Have 1+ Produced Feature(s)

[GordonsKitchen]

The backend currently allows generator combos to not have a listed produced feature. Generator combos will always need to have 1+ produced feature(s). I do not want to force all combos to have one listed, because of drafts and utilities that don't always need them.

[ldeluigi]

The fact that generator combos must have a result is an editor convention, but in theory a generator combos could be composed of a set of features that alone are sufficient to generate variants with all the necessary results, without adding a new one on top.

In addition, I can't implement this feature because Django unfortunately does not allow to cross-check fields of a Combo (in this case the kind) together with the related entities (in this case the produced features).

If you agree I'd like to close this issue