Add Serial Version

Closes gh-16163

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

@@ -90,6 +90,8 @@ import org.springframework.security.oauth2.jwt.TestJwts;
 import org.springframework.security.oauth2.server.resource.authentication.BearerTokenAuthentication;
 import org.springframework.security.oauth2.server.resource.authentication.BearerTokenAuthenticationToken;
 import org.springframework.security.oauth2.server.resource.authentication.JwtAuthenticationToken;
+import org.springframework.security.saml2.provider.service.authentication.DefaultSaml2AuthenticatedPrincipal;
+import org.springframework.security.saml2.provider.service.authentication.TestSaml2Authentications;
 import org.springframework.security.web.authentication.WebAuthenticationDetails;
 import org.springframework.security.web.authentication.preauth.PreAuthenticatedAuthenticationToken;
 
@@ -232,6 +234,10 @@ class SpringSecurityCoreVersionSerializableTests {
 			return token;
 		});
 
+		// saml2-service-provider
+		generatorByClassName.put(DefaultSaml2AuthenticatedPrincipal.class,
+				(r) -> TestSaml2Authentications.authentication().getPrincipal());
+
 		// web
 		generatorByClassName.put(PreAuthenticatedAuthenticationToken.class, (r) -> {
 			PreAuthenticatedAuthenticationToken token = new PreAuthenticatedAuthenticationToken(user, "creds",

saml2/saml2-service-provider/src/main/java/org/springframework/security/saml2/provider/service/authentication/DefaultSaml2AuthenticatedPrincipal.java

@@ -16,6 +16,7 @@
 
 package org.springframework.security.saml2.provider.service.authentication;
 
+import java.io.Serial;
 import java.io.Serializable;
 import java.util.Collections;
 import java.util.List;
@@ -32,6 +33,9 @@ import org.springframework.util.Assert;
  */
 public class DefaultSaml2AuthenticatedPrincipal implements Saml2AuthenticatedPrincipal, Serializable {
 
+	@Serial
+	private static final long serialVersionUID = -7601324133433139825L;
+
 	private final String name;
 
 	private final Map<String, List<Object>> attributes;