public void RemoveShare(Guid userId, Guid watchlistId, string symbol)
        {
            Validate.NotEmpty(userId, nameof(userId));
            Validate.NotEmpty(watchlistId, nameof(watchlistId));
            Validate.NotNullOrWhitespace(symbol, nameof(symbol));

            Watchlist watchlist = GetWatchlist(userId, watchlistId);

            watchlist.RemoveShare(symbol);
            _watchlistRepository.Save(watchlist);
        }