It turns out the "tax_rate" association isn't used and wasn't working.
Same for the "voucher" one, which I added to be consistent with existing
code.
Both of these weren't caught by the specs because you can't test associations
with a custome relation with 'shouda-matchers' see: https://github.com/thoughtbot/shoulda-matchers/issues/981
Voucher adjustment have complicated calculation that prevent us from
using Spree::Calculator, and we need to override CalculatedAdjustments
method, so no point using it.
We still keep the same methods to stay as consitent as possible in
regards to adjustments
Add missing, "inverse_of" and "dependent" options. Use :nullify as
for "dependent" because we would want to keep the adjustments on order
even if the voucher is deleted.
At the time when we can apply a voucher to an order (payment step) we
don't have any data on possible taxes and payment fees. These are
calculated when we move to the summary step. So voucher are applied in
two step:
- create an "open" voucher adjustment on the order when a customer enters
a voucher code.
- when we move to the summary step, recalulate the amount and
possible tax for the voucher adjustment, once taxes and payment fees
have been included in the order. And then close the original and update
order to reflect the changes
The checkout payment step will also show a warning.
The amount used is stored in the adjustment created, so we will be able
to track how much has been used down the line.
