Add setup cost to addons that have a returning cost

Verzoek

Currently it is not possible to add setup cost to addons. We have to choose between an one-time fee and a returning fee. They cannot be combined. For products this is already possible, for addons it is not. So for example Product: no setup fee and 20 dollars per month Addon A: 10 dollar setup fee and 5 dollars per month Addon b: no setup fee and 8 dollars per month Please add setup cost support to product addons.