public IActionResult createSignal([FromBody] SignalModel model)
        {
            var signal = _mapper.Map <Signal>(model);

            try
            {
                // create signal
                _signalService.create(signal);
                return(Ok());
            }
            catch (Exception ex)
            {
                // return error message if there was an exception
                return(BadRequest(new { message = ex.Message }));
            }
        }