public ActionResult <Appointment> DeleteAppointment(string id)
        {
            var appointment = DataStorage.GetAppointment(id);

            if (PermissionsService.AllowEditAppointment(CurrentUser, appointment))
            {
                DataStorage.DeleteAppointment(appointment);
                return(Ok(new { Message = "Success" }));
            }
            return(BadRequest(new { ErrorText = "Not Allowed" }));
        }