Refactored commerce models to remove language prefixes from status choices, improved order and payment validation, and enforced business rules for payment and shipping combinations. Updated order item and cart calculations to use VAT-inclusive prices, added unique constraints and indexes to reviews, and improved stock management logic. Added new Stripe client methods for session and refund management, and updated Zasilkovna and Deutsche Post models for consistency. Minor fixes and improvements across related tasks, URLs, and configuration models.
Added Deutsche Post as a shipping carrier, including new models, admin, serializers, and API client integration. Updated Carrier and SiteConfiguration models to support Deutsche Post, including shipping price and API credentials. Added requirements for the Deutsche Post API client and dependencies.