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

extensions/guacamole-auth-jdbc/modules/guacamole-auth-jdbc-base/src/main/java/org/apache/guacamole/auth/jdbc/InjectedAuthenticationProvider.java

@@ -104,6 +104,13 @@ public abstract class InjectedAuthenticationProvider implements AuthenticationPr
                 authenticatedUser, credentials);
     }
 
+    @Override
+    public UserContext decorate(UserContext context,
+            AuthenticatedUser authenticatedUser, Credentials credentials)
+            throws GuacamoleException {
+        return context;
+    }
+
     @Override
     public void shutdown() {
         // Do nothing