ProductPrice gains meta.percent_off support: percentOff()/isPercentage() and
effectiveAmount($base) — a percentage price resolves against a base (the
product's cheapest standalone price), so it can express e.g. '90% off with
Full Seat' rather than a fixed amount. Product::resolvePriceFor now ranks the
eligible prices by EFFECTIVE amount (percentage-aware) and returns the cheapest,
so a product linked to multiple prerequisites with different fixed/percentage
discounts always resolves to the cheapest the buyer qualifies for. Adds
ProductPrice::setConditionalPricing($requires, $percentOff, $label) — a
merge-safe authoring seam host admin UIs can call instead of hand-poking meta.
Add a generic conditional-pricing mechanic: a ProductPrice may carry
meta.requires (e.g. {"role":"seat"}) so it only applies to buyers who
already hold a prerequisite (loyalty / bundle pricing). Product::resolvePriceFor
returns the cheapest price the buyer is eligible for, delegating the
'does the buyer satisfy this requirement' test to a host-bound
EntitlementChecker contract. Defaults to DenyAllEntitlementChecker so an
unconfigured host never leaks a discount. Adds requires()/isConditional()/
requiresLabel()/requiresSatisfiedBy() and conditional()/standalone() scopes.
Fabian @ Blax Software