feat: Implement inventory policy for product variants

- Introduced InventoryPolicy enum to manage tracked and unlimited inventory types.
- Updated ProductVariant model to include inventory_policy and cantidad_vendida attributes.
- Modified addItem and updateItem methods in Cart to check available quantity based on inventory policy.
- Added migration to include inventory_policy and cantidad_vendida in productos_variantes table.
- Enhanced tests to validate inventory behavior for both tracked and unlimited policies.
- Updated various request and resource classes to handle new inventory fields.

app/Domains/Catalog/Enums/InventoryPolicy.php

@@ -0,0 +1,9 @@
+<?php
+
+namespace App\Domains\Catalog\Enums;
+
+enum InventoryPolicy: string
+{
+    case Tracked = 'tracked';
+    case Unlimited = 'unlimited';
+}