The Billig shipping script, named 'Export_Billig' in the Airtox File, is for sending shipping orders to Billig (BA) for processing. It runs as a MW script and uses CURL to send shipping orders over tcp/http. It is triggered by selecting Sales Invoices and pressing the “Export Billig” button.

• MW Sales Invoice Sending: Sends selected sales invoices to the Billig API.
• Checks Sales Invoices not already processed: Uses Transaction field user_4. Puts a timestamp if already sent. err:err text if error.
• Validates Delivery Addresses: Checks the delivery address meets criteria. More info below
• Validates Country 2 Char representation: Billig API uses 2 Char country digits for addresses
• TODO: Add more feature text

• mw_to_ubl.rs: MW → UBL/Edimondo export logic.
• ubl_to_mw.rs: Edimondo → MW import logic.
• mw.rs: MW API communication.
• edimondo.rs: Edimondo API communication.
• invoice.rs, order.rs: UBL document construction and parsing.
• export.rs, operations.rs: MW transaction and detail handling.
• db.rs: Database operations for exports/imports.
• config.rs: Configuration management.
• utilities.rs: Utility functions.

main.rs calls `start_server` which runs the main service loop.