Add Serializable for AssertingPartyDetails

Author: ngocnhan-tran1996

saml2/saml2-service-provider/src/main/java/org/springframework/security/saml2/provider/service/registration/RelyingPartyRegistration.java

@@ -460,6 +460,8 @@ public static Builder withRelyingPartyRegistration(RelyingPartyRegistration regi
 	 */
 	public static class AssertingPartyDetails implements AssertingPartyMetadata {
 
+		private static final long serialVersionUID = SpringSecurityCoreVersion.SERIAL_VERSION_UID;
+
 		private final String entityId;
 
 		private final boolean wantAuthnRequestsSigned;