feat: add total field to purchases and update related logic for payment processing

app/Domains/Purchase/Services/CheckoutService.php

@@ -29,6 +29,10 @@ class CheckoutService
                 ]);
             }
 
+            $cartItems->load('variant.product');
+            $cart->setRelation('items', $cartItems);
+            $totalAmount = $cart->getTotalAmount();
+
             /** @var Purchase $purchase */
             $purchase = Purchase::query()->updateOrCreate(
                 [
@@ -41,6 +45,7 @@ class CheckoutService
                     ...$purchaseData,
                     'payment_status' => 'pending',
                     'payment_method' => null,
+                    'total' => $totalAmount,
                 ]
             );