public async Task <IActionResult> Post([FromBody] BookCreateRequestModel book)
{
if (!await authorService.AuthorExistsAsync(book.AuthorId))
{
return(BadRequest("Author does not exist."));
}
int bookId = await bookService.CreateBookAsync(book.Title, book.Description, book.Price,
book.Copies, book.Edition, book.AuthorId, book.Categories);
return(this.Ok(bookId));
}