Placeholder donation stays in the cart if donate workflow is aborted

Problem/Motivation

Visiting /donate then going elsewhere on the website without following through with the donation leaves an empty order item in the cart.

This is especially a problem when there are other products in the store. Here's an example of a cart block on a site I'm working on:

Steps to reproduce

1. Go to /donate
2. Go to another page
3. Go to /cart

Proposed resolution

I'm not really sure. It's hard to detect when someone leaves a page. Perhaps the donation item is being added to the cart too early. Would it be better to have a donation product?

Remaining tasks

User interface changes

API changes

Data model changes