Fetch vertical eligibility data for a cart_item

Retrieve the details of buildings, staircases, floors, and otpIds for a cart_item so that the correct values can be provided when ordering. NB: Only applicable for entities with vertical_eligibility_needed product feature set to true. NB2: This endpoint will query some infrastructure operators synchronously. As a result it is more likely than others to exhibit speed issues and/or return an error.