feat: add productId for single-product selector model

src/contracts/checkout.ts

@@ -72,6 +72,16 @@ export const ConfirmCheckoutInputSchema = z.object({
 	 * Customer data provided at confirm time.
 	 */
 	customer: CustomerInputSchema.optional(),
+	/**
+	 * The selected product ID from the checkout's available products.
+	 * In the selector model, multiple products represent options to choose from,
+	 * and the user selects ONE product at confirm time.
+	 */
+	productId: z.string().optional(),
+	/**
+	 * Products array for CUSTOM pricing amounts only.
+	 * Use productId for standard product selection.
+	 */
 	products: z
 		.array(
 			z.object({

src/schemas/checkout.ts

@@ -57,7 +57,18 @@ const BaseCheckoutSchema = z.object({
 	 */
 	customer: CustomerOutputSchema.nullable(),
 	customerBillingAddress: z.record(z.any()).nullable(),
+	/**
+	 * Available product options for this checkout.
+	 * In the selector model, these represent choices the user can pick from.
+	 * The user selects ONE product, which is then stored in productId.
+	 */
 	products: z.array(CheckoutProductSchema).nullable(),
+	/**
+	 * The selected product ID (set after confirm).
+	 * In the selector model, this indicates which product the user chose
+	 * from the available products array.
+	 */
+	productId: z.string().nullable(),
 	providedAmount: z.number().nullable(),
 	totalAmount: z.number().nullable(),
 	discountAmount: z.number().nullable(),

tests/index.test.ts

@@ -60,6 +60,7 @@ describe('API Contract Index', () => {
             currency: 'USD',
           }],
         }],
+        productId: null,
         providedAmount: null,
         totalAmount: null,
         discountAmount: null,
@@ -191,4 +192,4 @@ describe('API Contract Index', () => {
       expect(contract.checkout.paymentReceived).toBeDefined();
     });
   });
-}); 
+});

tests/schemas/checkout.test.ts

@@ -23,6 +23,7 @@ const baseCheckoutData = {
   customer: null,
   customerBillingAddress: null,
   products: null,
+  productId: null,
   providedAmount: null,
   totalAmount: null,
   discountAmount: null,
@@ -383,4 +384,4 @@ describe('CheckoutSchema', () => {
       expect(result.success).toBe(false);
     });
   });
-}); 
+});