Amend backorder after cancellations

[mkllnk]

ℹ️ Funded Feature. Please track ALL ASSOCIATED WORK under the associated tracking code: #11678 DFC Orders

What? Why?

• Closes [DFC Orders] Cancelled Order does not reduce DFC Order quantities immediately #12876

The new job class blends code from the BackorderJob and the
CompleteBackorderJob for the specific case of adjusting quantities after
an order has been cancelled.

I would like to write a more general class which can be used for any
order amendmends but this was the quickest solution to cater for
currently running pilots.

What should we test?

• For @RaggedStaff:
• Checkout -> backorder is created.
• Cancel order -> backorder should be adjusted. If there was only one order then this results in an empty order, I think. I hope that doesn't cause trouble down the line. I could add a check and set it to cancelled?

Release notes

Changelog Category (reviewers may add a label for the release notes):

• User facing changes
• API changes (V0, V1, DFC or Webhook)
• Technical changes only
• Feature toggled

The title of the pull request will be included in the release notes.

Dependencies

Documentation updates

[RaggedStaff]

Ok, I've tested this & it seems to work (Shopify draft orders are correctly amended when an OFN order is cancelled)! 🎉

Cancel order -> backorder should be adjusted. If there was only one order then this results in an empty order, I think. I hope that doesn't cause trouble down the line. I could add a check and set it to cancelled?

This is a bit concerning... I think we do need to cancel the Order. Currently, when I remove all OFN Orders, the last item is left on the Shopify Order (this is a known issue - Shopify does not permit Orders without Line Items). The back Order then completes on OC close & submits that final product for delivery. 🫤

[rioug]

A bit hard to follow all the transformations, but it makes sense in the end. Nice one !

[dacook]

I have to admit I don't completely follow it, but I can see that it's been clearly specced and confirmed with manual testing already, and it needs to move forward.

Also I think it will be important to refactor in the not-too-distant future to ensure integrity (so we don't have duplicated code get out of sync) and make it easier for developers to use and understand it.

[dacook]

If the retail order and the backorder are both cancelled, why would the on_hand be changed?

[mkllnk]

This block is cancelling the OFN order. So when you cancel the order the local OFN stock is returned. The backorder hasn't been touch yet. That's done in the next block.

When the backorder is updated, there are two different methods. If the product is on demand then the local stock may be reduced again because we are cancelling part of the backorder at the same time. But when it's stock controlled, we don't touch the OFN stock. The backorder is only affected by the line item quantities while the stock is synced with the remote catalog.