refactor(checkout): keep source cart active

app/Domains/Purchase/Services/Checkout/StartCheckoutService.php

@@ -274,13 +274,6 @@ class StartCheckoutService
             );
         }
 
-        // The purchase owns the reservation until checkout finishes. The cart is
-        // retained so it can be restored if the purchase is cancelled or expires.
-        $cart->update([
-            'status' => 'checkout',
-            'guest_token' => null,
-        ]);
-
         return $this->loadPurchase($purchase);
     }
 
@@ -299,6 +292,14 @@ class StartCheckoutService
             ]);
         }
 
+        if ($cart->purchases()
+            ->whereIn('status', [Purchase::STATUS_CREATED, Purchase::STATUS_PENDING_PAYMENT])
+            ->exists()) {
+            throw ValidationException::withMessages([
+                'cart_id' => __('api.purchase.checkout_in_progress'),
+            ]);
+        }
+
         return $cart;
     }