Update API v5 methods

[gwinn]

Method summary:

• POST /api/v5/customers/create: method already existed; expanded customer and address DTOs to match current documentation, fixed the CustomerCreate example.
• POST /api/v5/orders/create: method already existed; expanded order, order item, company, and integration delivery DTOs.
• GET /api/v5/reference/delivery-types: method and DTOs were checked, no changes required.
• GET /api/v5/store/inventories: added explicit StoreInventories on top of existing Inventories, request/response aliases, and a test.
• GET /api/v5/store/offers: method was checked; existing StoreOffers and filters match the documentation.
• GET /api/v5/store/products: added explicit StoreProducts on top of existing Products, new filter fields, and a test.
• GET /api/v5/orders/packs: method already existed; fixed filter[stores][] encoding and expanded PackItem.
• POST /api/v5/orders/packs/create: method was checked; existing PackCreate uses the current Pack DTO.
• POST /api/v5/orders/packs/{id}/delete: method was checked, no changes required.
• POST /api/v5/orders/packs/{id}/edit: method was checked; existing PackEdit uses the current Pack DTO.
• POST /api/v5/orders/{externalId}/delivery/cancel: method was checked, no changes required.
• POST /api/v5/delivery/generic/{subcode}/tracking: added cost to DeliveryTrackingRequest and expanded the test.
• GET /api/v5/delivery/shipments: method and DTOs were checked, no changes required.
• POST /api/v5/delivery/shipments/create: method was checked; current fields are already supported through DeliveryShipment.
• GET /api/v5/delivery/shipments/{id}: method was checked; current fields are already supported through DeliveryShipment.
• POST /api/v5/delivery/shipments/{id}/edit: method was checked; current fields are already supported through DeliveryShipment.

Backward compatibility:

• ProductsFilter.Groups changed from string to []int to encode filter[groups][] according to the documentation.
• PacksFilter.Stores now encodes as filter[stores][], changing the query string for this filter.
• Several exported DTOs gained new fields; this is compatible for keyed composite literals, but users with unkeyed composite literals may need to update their code.