public IHttpActionResult Post([FromBody] Topic topic)
        {
            if (topic == null)
            {
                return(BadRequest());
            }

            topic.Created = DateTime.UtcNow;
            _repo.AddTopic(topic);
            if (!_repo.Commit())
            {
                return(BadRequest());
            }
            return(Created <Topic>("", topic));
        }