public IHttpActionResult PostBooksByAuthor(string authorFirstName, string authorLastName)
 {
     try
     {
         BookService service = CreateBookService();
         if (!service.AddBooksByAuthor(authorFirstName, authorLastName))
         {
             return(InternalServerError());
         }
         return(Ok());
     }
     catch (Exception e)
     {
         return(BadRequest(e.Message));
     }
 }