/// <summary>
        /// Her bliver vores ønskede data gemt i vores database.
        /// </summary>
        /// <param name="billetId"></param>
        /// <param name="kundeId"></param>
        /// <param name="antalBorn"></param>
        /// <param name="antalStuderende"></param>
        /// <param name="antalVoksne"></param>
        /// <param name="dateTime"></param>
        /// <param name="pris"></param>
        /// <param name="sejltur"></param>
        // gemmer alle værdier i databasen
        public void Add(int antalBorn, int antalStuderende, int antalVoksne, DateTime dateTime, decimal pris, bool sejltur, string email, string navn, string telefonNr)
        {
            Kunde newKunde = new Kunde(email, navn, telefonNr);

            Kunder.Add(newKunde);
            PersistencyService.SaveKunderAsJsonAsync(newKunde);
            Billet newBillet = new Billet(PersistencyService.ID, antalBorn, antalStuderende, antalVoksne, new DateTime(dateTime.Year, dateTime.Month, dateTime.Day), pris, sejltur);

            Billeter.Add(newBillet);
            PersistencyService.SaveBilleterAsJsonAsync(newBillet);
        }
        /// <summary>
        /// LoadKunderAsync loader data fra vores database tabel "kunder".
        /// </summary>
        public async void LoadKunderAsync()
        {
            var kunder = await PersistencyService.LoadKunderFromJsonAsync();

            if (kunder != null)
            {
                foreach (var k in Kunder)
                {
                    Kunder.Add(k);
                }
            }
            else
            {
                //Data til testformål
                Kunder.Add(new Kunde("Email1", "Navn1", "12345678"));
                Kunder.Add(new Kunde("Email2", "Navn2", "12345678"));
            }
        }