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/Purchase/Services/CheckoutService.php

@@ -97,6 +97,15 @@ class CheckoutService
     public function confirmPurchase(Purchase $purchase): void
     {
         DB::transaction(function () use ($purchase): void {
+            /** @var Purchase $purchase */
+            $purchase = Purchase::query()
+                ->lockForUpdate()
+                ->findOrFail($purchase->getKey());
+
+            if ($purchase->items()->exists()) {
+                return;
+            }
+
             /** @var Cart|null $cart */
             $cart = $purchase->cart()->lockForUpdate()->first();
 
@@ -114,10 +123,6 @@ class CheckoutService
                 ]);
             }
 
-            if ($purchase->items()->exists()) {
-                return;
-            }
-
             $cartItems->load('variant.product');
             $variants = $this->resolveTenantVariants($purchase->tenant, $cartItems);
             $purchaseItemsPayload = $this->buildPurchaseItemsPayload($cartItems, $variants);
@@ -158,7 +163,7 @@ class CheckoutService
 
     /**
      * @param  Collection<int, CartItem>  $cartItems
-     * @return \Illuminate\Support\Collection<int, ProductVariant>
+     * @return Collection<int, ProductVariant>
      */
     protected function resolveCheckoutCart(Tenant $tenant, int $userId, int $cartId): Cart
     {
@@ -218,7 +223,7 @@ class CheckoutService
             $quantity = (int) $item->cantidad;
 
             try {
-                $variant->confirmReservedStock($quantity);
+                $variant->buy($quantity);
             } catch (\InvalidArgumentException $exception) {
                 throw ValidationException::withMessages([
                     'cart_id' => 'The selected cart has inconsistent stock state.',