v2.4.0

[2.4.0] - 2026-09-22

Added

• A plan can carry a display price. Migration 009 adds price_amount (minor units),
  price_currency (ISO 4217) and billing_interval (day, week, month, year) to
  subscription_plans, accepted on create, patch and config import, all three or none. For a
  pricing page or plan picker to say what a plan costs; the gateway still decides what is charged.
• PlanPurchasability::forGateway() returns each plan's price_amount, price_currency and
  billing_interval (null when unset), so a plan picker can show the cost.
• A plan changed at the provider follows locally. A subscription.updated event whose price
  (gateway_price_id) belongs to another plan in the subscription's scope, by that plan's
  provider_identifiers for the gateway, moves the subscription to that plan and its entitlements.
  An unknown price changes nothing.