Order Creation: Add test coverage for order-related gaps in the Yosemite layer

[rachelmcr]

Closes: #6508

Description/Changes

While checking test coverage for Order Creation, we found a couple order-related gaps in the Yosemite layer.

• OrderFactory.deletedShippingLine wasn't exercised in testing. This is because we weren't using it to remove the shipping line from an order. ShippingInputTransformer now uses it to update the order when a shipping line is removed, and it is exercised in test_new_input_deletes_shipping_line_from_order() in ShippingInputTransformerTests.
• OrderNoteAction.addOrderNote had no test coverage. This isn't used in Order Creation, but it's worth adding coverage since the gap was identified. There are now tests in OrderNoteStoreTests to confirm that the expected note is returned and persisted, and that network errors are handled.

Testing

Confirm tests pass in CI.

You can also test the shipping line change as follows:

1. Go to the Orders tab and create a new order.
2. Select "Add Shipping", add a shipping amount, and tap Done.
3. On the New Order screen, once the order syncs remotely, tap "Shipping."
4. Select "Remove Shipping from Order."
5. Tap "Create" and confirm the order is created without any shipping.

Submitter Checklist

Update release notes:

• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[ealeksandrov]

Thanks for noticing and fixing the gaps in tests! LGTM

(Data?, Error?) manipulation instead of Result feels ancient now :)