Add Product::TAX_CLASS_MULTI_PURPOSE_VOUCHER and TaxService::ratesFor($product, ...),
which applies no tax rate to a product whose tax class is untaxed at sale
(config shop.tax.untaxed_classes, default the multi-purpose voucher). Under EU
VAT (Directive Art. 30a/30b, DE § 3 Abs. 15 UStG) selling a multi-purpose
voucher is not a taxable supply; VAT is due when it is redeemed, on the full
price of what it pays for. rates() is unchanged; ratesFor() is additive.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Blax\Shop\Services\TaxService::rates($exempt, $rates=null) is one source of
truth that turns "which rate(s)" (config shop.tax.rates or an explicit list)
and "is this customer exempt" into the array Stripe expects. It fails loud
(TaxRateNotConfiguredException) when shop.tax.require is set and no rate is
configured for a non-exempt charge, instead of silently billing 0% VAT.
New config('shop.tax') block (SHOP_TAX_RATES / SHOP_TAX_REQUIRE). Unit tested.
Consumers (learn-atc #1509) delegate getApplicableTaxRates() here so no path
can apply the rate twice (Stripe rejects duplicate tax rates) or drop VAT to 0%.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Fabian @ Blax Software