public SendTrainingReminderHandler(
     IClock clock,
     IAggregateStore aggregateStore,
     ITrainingRepository repo,
     IEmailService emailService,
     IOptions <Config> options,
     IFluidTemplateRenderer fluidTemplateRenderer)
 {
     _repo                  = repo ?? throw new ArgumentNullException(nameof(repo));
     _clock                 = clock ?? throw new ArgumentNullException(nameof(clock));
     _aggregateStore        = aggregateStore ?? throw new ArgumentNullException(nameof(aggregateStore));
     _emailService          = emailService ?? throw new ArgumentNullException(nameof(emailService));
     _options               = options ?? throw new ArgumentNullException(nameof(options));
     _fluidTemplateRenderer = fluidTemplateRenderer ?? throw new ArgumentNullException(nameof(fluidTemplateRenderer));
 }