- Introduced `SalesDocumentFlowService` to manage the lifecycle of sales documents, including packing slips and invoices.
- Implemented methods for processing orders, generating invoices, and handling packing slips based on order status.
- Updated `SalesOrdersService`, `PackingSlipsService`, and `SalesInvoicesService` to integrate with the new document flow service.
- Added new methods for marking drafts processed and checking if invoices are on sales plans.
- Enhanced existing services and repositories to support new functionalities, including status transitions and related document management.
- Updated DTOs to include new fields for packing slip and invoice IDs in sales order responses.
- Added unit tests for the new service and updated existing tests to cover new functionalities.
