public async Task<IHttpActionResult> SaveBook(BookModel bookModel)
        {
            if (ModelState.IsValid)
            {
                var entity = new Book();
                entity.InjectFrom(bookModel);

                return Ok(await _repository.Save(entity));
            }
            var errors = ModelState.Values.SelectMany(x => x.Errors);
            return BadRequest(Helper.GenerateModelStateError(errors));
        }