Track shared subscriptions

add the ability to enter details for shared subscriptions and change the monthly value accordingly. e.g. I have a duolingo family sub for 120€ p.a., but I share it with 4 other people, so I only effectively pay 20€ p.a.

I'd like to be able to enter the full 120€ into the sub details (because, that is what I am being charged/what I find on my credit card) but I personally don't actually spend 120€, so it should show differently in the stats