public async Task <IActionResult> VolunteersReturning([FromQuery] DateModel model)
        {
            var user = await userManager.GetUserAsync(User);

            if (user == null ||
                !(await userManager.IsInRoleAsync(user, UserHelpers.UserRoles.Staff.ToString())))
            {
                return(Utilities.ErrorJson("Not authorized."));
            }

            if (model.Date == DateTime.MinValue)
            {
                return(Utilities.GenerateMissingInputMessage("date"));
            }

            try
            {
                AnalyticsRepository repo = new AnalyticsRepository(configModel.ConnectionString);

                return(new JsonResult(new
                {
                    Count = repo.GetNumReturningVolunteers(model)
                }));
            }

            catch (Exception exc)
            {
                return(new JsonResult(new
                {
                    Error = exc.Message,
                }));
            }
        }