[Shopify] Handle deleted fulfillment service location in Shopify

[onbuyuka]

Problem

When a fulfillment service location is deleted in Shopify but the corresponding Shpfy Shop Location record still exists in Business Central, the GetLocation GraphQL query returns {"data":{"location":null}}. The code attempted to parse data.location.fulfillmentService as a single path, which fails because the null location token cannot be traversed to reach fulfillmentService. This left a stale record with Fulfillment Service Id = 0, causing UpdateFulfillmentServiceCallbackUrl to proceed with an invalid ID in the UpdateFulfillmentService GraphQL mutation.

Solution

GetFulfillmentService: Split the JSON parsing into two steps. First resolve data.location — if it's null (location no longer exists in Shopify), delete the stale ShopLocation record (which cascades to related Shpfy Shop Inventory records) and exit. Then separately resolve fulfillmentService within the location object.

UpdateFulfillmentServiceCallbackUrl: After calling GetFulfillmentService, recheck Fulfillment Service Id. If it's still 0 (record was deleted or service couldn't be resolved), exit before attempting the update mutation. This provides defense in depth against calling the Shopify API with an invalid ID.

Fixes AB#622988