Expanded DeutschePostOrder and DeutschePostBulkOrder models to support full Deutsche Post API integration, including authentication, order creation, finalization, tracking, cancellation, and label/document generation. Added new fields for label PDFs and bulk paperwork, improved country mapping, and implemented comprehensive validation and utility methods. Updated serializers to expose new fields and computed properties. Added HTML templates for individual and bulk shipping labels.
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.
