For some reason the order objects were stale here when calling order.update! from either a payment or shipment callback, which was overwriting those states as nil on the order.
This new class lets us [Branch by
abstraction](https://www.martinfowler.com/bliki/BranchByAbstraction.html)
by encapsulating an order's balance. As a result, that's the only place
where we need to check the feature toggle, instead of every place where
`#outstanding_balance` is called (quite some). That would be very hard
to review and it'd be more likely to introduce bugs.
What I like about this is that we also managed to group together the
data and logic that we had spread in a few places and have it nicely
encapsulated. So, where we had a number, we'll now have an object.
Once we fully change all `#outstanding_balance` consumers to use this
new abstraction we'll be able to remove the methods this class replaces.
These are: `Spree::Order#outstanding_balance?`,
`Spree::Order#display_oustanding_balance` and
`OrderHelper.outstanding_balance_label`.
This is just the first step. I'll follow this up with a PR per
page/mailer/whatever where we use the balance to replace it with an
instance of `OrderBalance`. That is, splitting up what I explored in
https://github.com/openfoodfoundation/openfoodnetwork/pull/6959 but in
very small and manageable pieces.
We set this value to `true` unconditionally in an initializer, and then check the value in various places via Spree::Config. It's never false, and it's not configurable, so we can just drop it and remove the related conditionals. 🔥
This was triggering two separate updates, and each of those updates could trigger callbacks, and those could trigger other callbacks. Here we're doing the same thing, but with one update.
This model concerns helps us put together this related methods. Although
it doesn't provide any encapsulation yet, it makes a bit easier to
consider them all next time we need to change this implementation
somehow. It's a bit of an illusion but it feels like we are making this
God object model a bit smaller.
It also gives more room for documentation that will aid future devs.
