GUACAMOLE-96: Add API support for augmenting functionality of other extensions.

guacamole/src/main/java/org/apache/guacamole/extension/AuthenticationProviderFacade.java

@@ -158,6 +158,20 @@ public class AuthenticationProviderFacade implements AuthenticationProvider {
         
     }
 
+    @Override
+    public UserContext decorate(UserContext context,
+            AuthenticatedUser authenticatedUser,
+            Credentials credentials) throws GuacamoleException {
+
+        // Do nothing if underlying auth provider could not be loaded
+        if (authProvider == null)
+            return context;
+
+        // Delegate to underlying auth provider
+        return authProvider.decorate(context, authenticatedUser, credentials);
+
+    }
+
     @Override
     public void shutdown() {
         if (authProvider != null)