serial version uid fix for serializable classes

Author: rng70-or

oauth2_http/java/com/google/auth/oauth2/ExternalAccountMetricsHandler.java

@@ -36,6 +36,8 @@
  * credentials.
  */
 class ExternalAccountMetricsHandler implements java.io.Serializable {
+  private static final long serialVersionUID = 7825203615911901249L;
+  
   private static final String SOURCE_KEY = "source";
   private static final String IMPERSONATION_KEY = "sa-impersonation";
   private static final String CONFIG_LIFETIME_KEY = "config-lifetime";

oauth2_http/java/com/google/auth/oauth2/OAuth2Credentials.java

@@ -497,6 +497,8 @@ public Builder toBuilder() {
 
   /** Stores an immutable snapshot of the accesstoken owned by {@link OAuth2Credentials} */
   static class OAuthValue implements Serializable {
+    private static final long serialVersionUID = -7269184394646019967L;
+  
     private final AccessToken temporaryAccess;
     private final Map<String, List<String>> requestMetadata;