[Shopify] Product metafields extensibility

[onbuyuka]

Summary

This PR adds extensibility for Shopify product metafields, allowing external developers to programmatically manage metafields through a public facade codeunit and integration events.

Problem

External developers cannot programmatically:

• Retrieve metafield definitions for products/variants
• Add metafields with values when missing
• Force-sync metafields to Shopify outside of the standard item sync

Solution

Implemented a public facade pattern (similar to existing Shpfy Product and Shpfy Orders codeunits) for metafield management.

Changes

• ShpfyMetafields.Codeunit.al - Public facade codeunit with:

  • GetMetafieldDefinitions(ParentTableNo, OwnerId, ShopCode) - Retrieve metafield definitions from Shopify
  • SyncMetafieldToShopify(Metafield, ShopCode): BigInteger - Sync a single metafield to Shopify
  • SyncMetafieldsToShopify(ParentTableNo, OwnerId, ShopCode) - Sync all metafields for a resource

• ShpfyProductEvents.Codeunit.al

  • Added OnBeforeUpdateProductMetafields(ProductId: BigInteger) integration event

• ShpfyProductExport.Codeunit.al

  • Raises OnBeforeUpdateProductMetafields event before syncing metafields
  • Refactored to use public facade for metafield operations

• ShpfyMetafields.Page.al

  • Added "Sync to Shopify" action with multi-select support
  • Refactored to use public facade for all metafield operations

• ShpfyCustomerExport.Codeunit.al

  • Refactored to use public facade for metafield sync

• ShpfyCompanyExport.Codeunit.al

  • Refactored to use public facade for metafield sync

Work Item(s)

Fixes AB#617035