Add channel liable tax tracking for Shopify orders

[AndreiPanko]

Summary

• include Shopify channelLiable flag in all order and shipment GraphQL queries
• persist channel liable taxes on orders to import and headers with UI exposure
• add comprehensive tests for channelLiable scenarios across staging and import flows

Testing

• Not run (requires Business Central test suite)

Fixes: AB#608939

[Copilot]

Pull Request Overview

This PR adds support for tracking Shopify's channel liable tax flag throughout the order handling process. Channel liable taxes indicate when a sales channel (rather than the merchant) is responsible for collecting and remitting taxes.

Key changes:

• Added Channel Liable field to order tax lines and Channel Liable Taxes calculated field to order headers
• Updated all GraphQL queries to retrieve the channelLiable field from Shopify
• Added comprehensive test coverage for all channelLiable scenarios (missing, true, false, null)

Reviewed Changes

Copilot reviewed 17 out of 17 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
ShpfyOrdersAPITest.Codeunit.al	Added 8 test procedures covering channelLiable flag handling in staging and import flows
ShpfyOrdersToImport.Table.al	Added Channel Liable Taxes boolean field to staging table
ShpfyOrderTaxLine.Table.al	Added Channel Liable boolean field to tax line table
ShpfyOrderHeader.Table.al	Added Channel Liable Taxes FlowField calculated from tax lines
ShpfySyncOrdersfromShopify.Report.al	Added Channel Liable Taxes to request filter fields
ShpfyOrdersToImport.Page.al	Added Channel Liable Taxes field to staging page UI
ShpfyOrders.Page.al	Added Channel Liable Taxes field to orders list page
ShpfyOrderTaxLines.Page.al	Added Channel Liable field to tax lines page
ShpfyOrder.Page.al	Added Channel Liable Taxes field to order detail page
ShpfyOrdersAPI.Codeunit.al	Added ContainsChannelLiableTax function to check first tax line
ShpfyImportOrder.Codeunit.al	Added channelLiable field extraction during tax line import
ShpfyGQL*.Codeunit.al (6 files)	Updated GraphQL queries to include channelLiable and adjusted expected costs

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