Can one somehow map supermarket trolleys?

Question

Can one somehow map/add the shed for supermarkt trolleys (when it is outside of the supermarket/building, commonly on the parking area somewhere)?

As a node:

amenity=shelter
shelter_type=shopping_cart

As an area/relation:

building=roof
note=shopping_cart

Although another suggestion is to use trolley_bay.

So what is finally the correct way?

Accepted Answer

As @SomeoneElse says, there's no official answer. So I'll give you my personal opinion, I like amenity=trolley_bay because:

Works for British English.
Not all of these are covered, so subtagging amenity=shelter isn't ideal (and you can always add other tags such as covered=yes if it is covered).
Same for using building (and adding data with the note key is not a good practice).
This is vague enough to work for shopping carts, luggage carts, and any kinds of carts/trolleys
It's used more than the other options I see in taginfo