public async Task <IActionResult> Index(int?collectionYear, int?period, CancellationToken cancellationToken)
        {
            var returnPeriod = await _periodService.ReturnPeriod(CollectionType, cancellationToken);

            var years = await _periodService.GetValidityYearsAsync(CollectionType, null, cancellationToken);

            var year         = collectionYear ?? returnPeriod.Year ?? 0;
            var periodNumber = period ?? returnPeriod.Period;

            var stateString = await _periodEndService.GetPrepStateAsync(year, periodNumber, CollectionType, cancellationToken);

            var state = _stateService.GetPrepState(stateString);

            var model = new ValidityPeriodViewModel
            {
                Year   = year,
                Period = periodNumber,
                PeriodEndInProgress = state.State.PeriodEndStarted && !state.State.PeriodEndFinished,
                AllYears            = years
            };

            return(View(model));
        }