fix: add available_stock update in StockUpdateService

[stefanpoensgen]

No description provided.

[Copilot]

Pull Request Overview

This PR adds an available_stock field update to the stock update operation in StockUpdateService. The change sets available_stock to the same value as the new stock level during stock updates.

Key Changes:

• Added available_stock field to the database update array, setting it equal to newStock

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[Copilot]

Setting available_stock to the same value as stock may be incorrect. In Shopware 6, available_stock typically represents the stock available for purchase (stock minus reserved/allocated stock from pending orders). By setting it directly to newStock, this change ignores any reserved stock that should be subtracted.

Consider either:

1. Fetching the current available_stock value in the query at line 62-76 and calculating the new available_stock based on the difference between old and new stock values: current_available_stock + ($newStock - $oldStock)
2. Removing this field from the update and letting Shopware's core mechanisms handle available_stock calculation
3. If the intention is to reset reserved stock, this should be documented and potentially require an explicit parameter

Suggested change

'available_stock' => $newStock,

[Copilot]

The new available_stock update behavior is not covered by any tests. Consider adding test cases that verify:

1. The available_stock field is updated correctly when stock changes
2. The relationship between stock and available_stock is maintained properly
3. Edge cases such as when there might be reserved stock

This is particularly important given the semantic difference between stock and available_stock in Shopware.