fix serialization tests

Author: slobodanadamovic

x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/security/authc/AuthenticationSerializationTests.java

@@ -117,7 +117,10 @@ public void testWriteToWithCrossClusterAccessThrowsOnUnsupportedVersion() throws
 
     public void testWriteToAndReadFromWithCloudApiKeyAuthentication() throws Exception {
         final Authentication authentication = Authentication.newCloudApiKeyAuthentication(
-            AuthenticationResult.success(new User(randomAlphanumericOfLength(5), "superuser"), Map.of()),
+            AuthenticationResult.success(
+                new User(randomAlphanumericOfLength(5), "superuser"),
+                Map.of(AuthenticationField.API_KEY_ID_KEY, "test-api-key-id")
+            ),
             randomAlphanumericOfLength(10)
         );
 
@@ -134,7 +137,10 @@ public void testWriteToAndReadFromWithCloudApiKeyAuthentication() throws Excepti
 
     public void testWriteToWithCloudApiKeyThrowsOnUnsupportedVersion() {
         final Authentication authentication = Authentication.newCloudApiKeyAuthentication(
-            AuthenticationResult.success(new User(randomAlphanumericOfLength(5), "superuser"), Map.of()),
+            AuthenticationResult.success(
+                new User(randomAlphanumericOfLength(5), "superuser"),
+                Map.of(AuthenticationField.API_KEY_ID_KEY, "test-api-key-id")
+            ),
             randomAlphanumericOfLength(10)
         );