Stock Level Update endpoints should include sub-clients argument

We're having an issue receiving updates for stock-levels. The issues is that existing endpoints does not include subclient's products in the update list, but we need those in order to keep our data sync.

These two endpoints for stock level updates (we're actually using only the first one):

api/Product/StockLevels/UpdatedSince?FromDate

api/Product/StockLevelsByWarehouse?WarehouseId=3&LastUpdatedSince=2025-01-20

don't have any IncludeSubclients arguments.

I know about https://api.mintsoft.co.uk/swagger/ui/index#!/Product/Product_GetStockLevels - we're using it for the initial load of all products. This approach takes more than an hour when making sequential requests to fetch all the data, as each product must be queried separately. We could try running it in multiple threads, but that is far from an optimized way to fetch stock level updates. Running it multithreaded would also increase the workload on Mintsoft's API.