public async Task <IEnumerable <Participant> > CreateRange([FromBody] ParticipantRange range)
        {
            ApplicationUser user = await _userManager.GetUserAsync(HttpContext.User);

            IEnumerable <Participant> created = await _participantService.CreateRangeAsync(range, user, ModelState.AddModelError);

            if (created == null)
            {
                return(null);
            }

            return(created);
        }