Retroactive order uploads update

[pukhalski]

- Do you want to request a feature or report a bug?
Feature

- What is the current behavior?
User doesn't see any product uploads (or changes) if they were added after the actual purchase.

- If the current behavior is a bug, please provide the steps to reproduce.
Purchase a digital product, then add another upload to it. User won't see it.

- What is the expected behavior?
Product uploads are retroactively propagated to all orders.

[biilmann]

We have a script that'll do this on demand for any order now. So for a start, let us know when it's needed and we'll trigger it.

I'll work to get that running as a background task in gocommerce itself.

[pukhalski]

@biilmann, can you share it? Or if it's not going to take a lot of time, I'd grab it from gocommerce.

[mraerino]

The endpoint introduced in #184 /orders/:order_id/downloads/refresh should enable you to give users a button for refreshing downloads in an order.
Closing this for now. Let me know if you need a different approach.