fix: sessionId test classes

Author: kieran-osgood-shopify

modules/@shopify/checkout-sheet-kit/ios/ShopifyCheckoutSheetKit+EventSerialization.swift

@@ -100,9 +100,7 @@ internal enum ShopifyEventSerialization {
             "id": event.id,
             "method": event.method,
             "cart": encodeToJSON(from: event.cart),
-            "checkout": [
-                "id": event.checkout.id
-            ]
+            "sessionId": event.sessionId
         ]
     }
 

sample/ios/ReactNativeTests/RCTCheckoutWebViewTests.swift

@@ -407,7 +407,7 @@ class RCTCheckoutWebViewTests: XCTestCase {
                 subtotalAmount: "100.00",
                 totalAmount: "110.00"
             ),
-            checkout: Checkout(id: "checkout-123")
+            sessionId: "checkout-123"
         )
 
         checkoutWebView.checkoutDidStartSubmit(event: request)
@@ -439,7 +439,7 @@ class RCTCheckoutWebViewTests: XCTestCase {
         let request = CheckoutSubmitStartEvent.testInstance(
             id: "submit-registry-test",
             cart: createTestCart(),
-            checkout: Checkout(id: "checkout-registry")
+            sessionId: "checkout-123"
         )
 
         checkoutWebView.checkoutDidStartSubmit(event: request)
@@ -521,7 +521,7 @@ class RCTCheckoutWebViewTests: XCTestCase {
         let request = CheckoutSubmitStartEvent.testInstance(
             id: "submit-event-1",
             cart: createTestCart(),
-            checkout: Checkout(id: "checkout-1")
+            sessionId: "checkout-123"
         )
         checkoutWebView.checkoutDidStartSubmit(event: request)