public LoginPageModel(INavigationService navigationService,
                              IAccountService accountService)
        {
            this.accountService    = accountService;
            this.navigationService = navigationService;

            UsernameEntryViewModel = new LoginEntryViewModel("username", false);
            PasswordEntryViewModel = new LoginEntryViewModel("password", true);

            LogInButtonViewModel         = new ButtonViewModel("log in", OnLogin);
            CreateAccountButtonViewModel = new ButtonViewModel("create account", OnCreateAccount);
        }
        public ProfilePageModel(
            IAccountService accountService,
            ITrackedPeriodService trackedPeriodService,
            INavigationService navigationService,
            ViewAllPageModel viewAllPageModel,
            TimerPageModel timerPageModel)
        {
            this.accountService       = accountService;
            this.trackedPeriodService = trackedPeriodService;
            this.navigationService    = navigationService;
            this.viewAllPageModel     = viewAllPageModel;
            this.timerPageModel       = timerPageModel;

            UsernameEntryViewModel = new LoginEntryViewModel("username", isPassword: false);
            PasswordEntryViewModel = new LoginEntryViewModel("password", isPassword: true);

            UpdatePasswordButtonViewModel = new ButtonViewModel("update password", OnUpdatePasswordButtonPressed);
            ClearUserDataButtonViewModel  = new ButtonViewModel("clear data", OnClearDataButtonPressed);
            LogOutButtonViewModel         = new ButtonViewModel("log out", OnLogOutButtonPressed);
        }