/// <summary>
        /// Sends a request to Marvel's API, and returns comics found based on title,
        /// and issue number.
        /// </summary>
        /// <param name="title">The title of the <see cref="Comic"/></param>
        /// <param name="issueNumber">The issue number of the <see cref="Comic"/></param>
        /// <returns>An <see cref="IEnumerable{Comic}"/> of comic results.</returns>
        public async Task <IList <Comic> > GetByTitleAndIssueNumber(string title, string issueNumber)
        {
            // TODO: create & move this to a 'marvel client' project, and make a repository.
            MarvelResponse comicResponse = await _marvelClient.RequestComic(
                "/comics",
                $"title={title}&issueNumber={issueNumber}"
                );

            IEnumerable <MarvelComic> comicData = comicResponse
                                                  .Data
                                                  .Results
                                                  .AsEnumerable();

            if (comicData is null)
            {
                return(new List <Comic> ());;
            }

            var comics = comicData
                         .Select(marvelComic =>
                                 MapResponseToComic(marvelComic, comicResponse.Copyright))
                         .ToList();

            return(comics);
        }
        /// <summary>
        /// Fetches matching comic based on barcode isbn number.
        /// </summary>
        /// <param name="upc"></param>
        /// <returns></returns>
        public async Task <Comic> GetByCode(string upc)
        {
            MarvelResponse comicResponse = await _marvelClient.RequestComic("/comics", $"upc={upc}");

            MarvelComic comicData = comicResponse
                                    .Data
                                    .Results
                                    .FirstOrDefault();

            if (comicData is null)
            {
                return(new Comic());
            }

            Comic comic = MapResponseToComic(comicData, comicResponse.Copyright);

            return(comic);
        }