Update CHANGELOG and migration guide

CHANGELOG.md

@@ -108,6 +108,10 @@
   * American Express
     * Change parameters of `AmericanExpressGetRewardsBalanceCallback`
     * Add `AmericanExpressResult`
+  * Visa Checkout
+    * Change parameters of `VisaCheckoutCreateProfileBuilderCallback` and 
+      `VisaCheckoutTokenizeCallback`
+    * Add `VisaCheckoutProfileBuilderResult` and `VisaCheckoutTokenizeResult`
 
 ## 4.40.1 (2023-12-13)
 

v5_MIGRATION_GUIDE.md

@@ -17,6 +17,7 @@ basics for updating your Braintree integration from v4 to v5.
 1. [PayPal](#paypal)
 1. [Local Payment](#local-payment)
 1. [SEPA Direct Debit](#sepa-direct-debit)
+1. [Visa Checkout](#visa-checkout)
 
 ## Android API
 
@@ -508,4 +509,38 @@ class MyActivity : FragmentActivity() {
 -   override fun onSEPADirectDebitFailure(error: java.lang.Exception) {
 -        // handle error
 -   }
-}
+}
+```
+
+## Visa Checkout
+
+The Visa Checkout integration has been updated to improve result handling.
+
+```diff
+class MyActivity : FragmentActivity() {
+
+-   private lateinit var braintreeClient: BraintreeClient
+    private lateinit var visaCheckoutClient: VisaCheckoutClient
+
+    fun initializeClients() {
+-       braintreeClient = BraintreeClient(context, "TOKENIZATION_KEY_OR_CLIENT_TOKEN")
+-       visaCheckoutClient = VisaCheckoutClient(braintreeClient)
++       visaCheckoutClient = visaCheckoutClient(context, "TOKENIZATION_KEY_OR_CLIENT_TOKEN")
+    }
+
+    fun onPaymentButtonClick() {
+-       visaCheckoutClient.tokenize(request)
++       sepaDirectDebitClient.tokenize(request) { visaCheckoutResult ->
++           when(visaCheckoutResult) {
++               is (VisaCheckoutResult.Failure) -> { 
++                   // handle visaCheckoutResult.error
++               is (VisaCheckoutResult.Success) -> {      
++                   // handle visaCheckoutResult.nonce
++               }
++           }
++       }
+    }
+}
+```
+
+