public ObjectResult AddGeneVariantLiterature(
            int literatureId,
            int geneVariantId
            )
        {
            var geneVariantLiterature = new GeneVariantLiterature
            {
                GeneVariantId = geneVariantId,
                LiteratureId  = literatureId
            };

            _context.GeneVariantLiterature.Add(geneVariantLiterature);
            _context.SaveChanges();

            geneVariantLiterature = _context.GeneVariantLiterature
                                    .Include(gvl => gvl.Literature)
                                    .ThenInclude(l => l.AnnotationLiterature)
                                    .ThenInclude(al => al.Annotation)
                                    .Include(gvl => gvl.Literature)
                                    .ThenInclude(l => l.AuthorLiterature)
                                    .ThenInclude(al => al.Author)
                                    .Include(gvl => gvl.AnnotationGeneVariantLiterature)
                                    .ThenInclude(agvl => agvl.Annotation)
                                    .Single(gvl => gvl.Id == geneVariantLiterature.Id);

            return(Ok(_mapper.Map <GeneVariantLiteratureDto>(geneVariantLiterature)));
        }
        public ObjectResult AddGeneVariantLiterature(
            int geneVariantId,
            int literatureId
            )
        {
            var geneVariantLiterature = new GeneVariantLiterature
            {
                GeneVariantId = geneVariantId,
                LiteratureId  = literatureId
            };

            _context.GeneVariantLiterature.Add(geneVariantLiterature);
            var literatureEntity = _context.Literature
                                   .SingleOrDefaultAsync(m => m.Id == literatureId);

            return(Ok(_mapper.Map <LiteratureDto>(literatureEntity)));
        }