public async Task <IEnumerable <Workshop> > GetWorkshopsAsync(int groupId)
        {
            if (groupId <= 0)
            {
                throw new ArgumentException($"Argument {nameof(groupId)} can't be less or equal zero!");
            }

            var workshopsDtos = await workshopRepository.GetWorkshopsAsync(groupId);

            var workshops = new List <Workshop>();

            foreach (var workshopDto in workshopsDtos)
            {
                workshops.Add(workshopDto.ToWorkshop());
            }

            return(workshops);
        }