Make ForceAliasCreation nullable (#2170)

Author: peterrsongg

.autover/changes/1916e292-d131-4c9a-8036-0d7b68f0ce7a.json

@@ -0,0 +1,11 @@
+{
+  "Projects": [
+    {
+      "Name": "Amazon.Lambda.CognitoEvents",
+      "Type": "Patch",
+      "ChangelogMessages": [
+        "[Breaking Change] Fix issue around not handling null value during deserialization for `ForceAliasCreation` by making it nullable."
+      ]
+    }
+  ]
+}

Libraries/src/Amazon.Lambda.CognitoEvents/CognitoMigrateUserResponse.cs

@@ -1,4 +1,4 @@
-using System.Collections.Generic;
+using System.Collections.Generic;
 using System.Runtime.Serialization;
 
 namespace Amazon.Lambda.CognitoEvents
@@ -51,6 +51,6 @@ public class CognitoMigrateUserResponse : CognitoTriggerResponse
 #if NETCOREAPP3_1_OR_GREATER
         [System.Text.Json.Serialization.JsonPropertyName("forceAliasCreation")]
 #endif
-        public bool ForceAliasCreation { get; set; }
+        public bool? ForceAliasCreation { get; set; }
     }
 }