public ActionResult <int> QueueRecommendation(string userId, [FromBody] List <int> requestedTagIds)
        {
            if (userId is null || requestedTagIds is null)
            {
                return(BadRequest());
            }

            var queuedRecommendationId = _queue.QueueRecommendation(userId, requestedTagIds);

            return(queuedRecommendationId);
        }