/**
  * Register a new consumer configured with Consumer Key.
  *
  * @param owner Identifier of the owner that registers the consumer (user ID or similar).
  * @param key Consumer key.
  * @param secret Consumer key secret.
  * @param attributes Additional attributes (name-values pairs - to store additional information
  *     about the consumer, such as name, URI, description, etc.)
  * @return {@link Consumer} object for the newly registered consumer.
  */
 public Consumer registerConsumer(
     final String owner,
     final String key,
     final String secret,
     final MultivaluedMap<String, String> attributes) {
   final Consumer c = new Consumer(key, secret, owner, attributes);
   consumerByConsumerKey.put(c.getKey(), c);
   return c;
 }