public IHttpActionResult PostInstructor([FromBody] InstructorCreate model)
        {
            if (!ModelState.IsValid)
            {
                return(BadRequest(ModelState));
            }

            var svc = new InstructorService();

            if (!svc.CreateInstructor(model))
            {
                return(InternalServerError());
            }

            return(Ok("Instructor successfully added."));
        }