Implement Serializable for PublicKeyCredentialUserEntity

Closes gh-16273

Signed-off-by: Tran Ngoc Nhan <ngocnhan.tran1996@gmail.com>

Author: ngocnhan-tran1996

config/src/test/java/org/springframework/security/SpringSecurityCoreVersionSerializableTests.java

@@ -191,6 +191,9 @@
 import org.springframework.security.web.firewall.RequestRejectedException;
 import org.springframework.security.web.server.firewall.ServerExchangeRejectedException;
 import org.springframework.security.web.session.HttpSessionCreatedEvent;
+import org.springframework.security.web.webauthn.api.Bytes;
+import org.springframework.security.web.webauthn.api.ImmutablePublicKeyCredentialUserEntity;
+import org.springframework.security.web.webauthn.api.TestPublicKeyCredentialUserEntity;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.fail;
@@ -508,6 +511,11 @@ class SpringSecurityCoreVersionSerializableTests {
 				(r) -> new AuthenticationSwitchUserEvent(authentication, user));
 		generatorByClassName.put(HttpSessionCreatedEvent.class,
 				(r) -> new HttpSessionCreatedEvent(new MockHttpSession()));
+
+		// webauthn
+		generatorByClassName.put(Bytes.class, (r) -> Bytes.random());
+		generatorByClassName.put(ImmutablePublicKeyCredentialUserEntity.class,
+				(r) -> TestPublicKeyCredentialUserEntity.userEntity().build());
 	}
 
 	@ParameterizedTest

config/src/test/resources/serialized/6.5.x/org.springframework.security.web.webauthn.api.Bytes.serialized

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2024 the original author or authors.
+ * Copyright 2002-2025 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,6 +16,7 @@
 
 package org.springframework.security.web.webauthn.api;
 
+import java.io.Serializable;
 import java.security.SecureRandom;
 import java.util.Arrays;
 import java.util.Base64;
@@ -28,7 +29,9 @@
  * @author Rob Winch
  * @since 6.4
  */
-public final class Bytes {
+public final class Bytes implements Serializable {
+
+	private static final long serialVersionUID = -3278138671365709777L;
 
 	private static final SecureRandom RANDOM = new SecureRandom();
 

config/src/test/resources/serialized/6.5.x/org.springframework.security.web.webauthn.api.ImmutablePublicKeyCredentialUserEntity.serialized

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2024 the original author or authors.
+ * Copyright 2002-2025 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -28,6 +28,8 @@
  */
 public final class ImmutablePublicKeyCredentialUserEntity implements PublicKeyCredentialUserEntity {
 
+	private static final long serialVersionUID = -3438693960347279759L;
+
 	/**
 	 * When inherited by PublicKeyCredentialUserEntity, it is a human-palatable identifier
 	 * for a user account. It is intended only for display, i.e., aiding the user in

web/src/main/java/org/springframework/security/web/webauthn/api/Bytes.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2024 the original author or authors.
+ * Copyright 2002-2025 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,6 +16,8 @@
 
 package org.springframework.security.web.webauthn.api;
 
+import java.io.Serializable;
+
 /**
  * <a href=
  * "https://www.w3.org/TR/webauthn-3/#dictdef-publickeycredentialuserentity">PublicKeyCredentialUserEntity</a>
@@ -27,7 +29,7 @@
  * @since 6.4
  * @see org.springframework.security.web.webauthn.management.WebAuthnRelyingPartyOperations#authenticate(org.springframework.security.web.webauthn.management.RelyingPartyAuthenticationRequest)
  */
-public interface PublicKeyCredentialUserEntity {
+public interface PublicKeyCredentialUserEntity extends Serializable {
 
 	/**
 	 * The <a href=