public IEnumerable <AllTopicsResult> Handle(AllTopicsQuery query)
        {
            var response = _dbContext
                           .Set <Topic>()
                           .Project().To <AllTopicsResult>();

            return(response);
        }
        public IHttpActionResult GetTopics()
        {
            var query = new AllTopicsQuery();

            var response = _mediator.Send(query);

            return(Ok(response));
        }