public async Task <Document> SaveDocumentAsync(Stream fileStream, string fileName, long fileSize)
        {
            var id           = Guid.NewGuid().ToString();
            var fileLocation = await _contentStorage.SaveFile(fileStream, id + Path.GetExtension(fileName));

            var documentsCount = _documentsRepository.GetDocumentsCount();

            var document = new Document
            {
                Id       = id,
                Name     = fileName,
                FileSize = fileSize,
                Location = fileLocation,
                Position = documentsCount + 1
            };

            return(await _documentsRepository.AddDocumentAsync(document));
        }