Configure client id and client secret in the config file

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=224158599

java/google/registry/config/RegistryConfigSettings.java

@@ -182,6 +182,7 @@ public class RegistryConfigSettings {
 
   /** Configuration options for the registry tool. */
   public static class RegistryTool {
-    public String clientSecretFilename;
+    public String clientId;
+    public String clientSecret;
   }
 }