public IActionResult GetInstructorsByCategory([FromQuery] string category)
        {
            try
            {
                var instructorList = _instructorService.GetInstructorsByCategory(category);
                var result         = _mapper.Map <List <Instructor>, List <InstructorDTO> > (instructorList);

                return(Ok(result));
            }
            catch (Exception)
            {
                return(BadRequest("Error!"));
            }
        }