private void AddCar()
{
string id;
string brand;
Console.Write("Enter ID of car:");
id = Console.ReadLine();
Console.Write("Enter Brand of car:");
brand = Console.ReadLine();
carRental.AddCar(new Car(id, brand));
}
static void GenerateTestCarRental()
{
CarRentalSystem carRental = new CarRentalSystem();
Client clien1 = new Client("111", "Mr.Jonson");
Client clien2 = new Client("222", "Mr.Anderson");
Client clien3 = new Client("333", "Mr.Pietersen");
carRental.AddClient(clien1);
carRental.AddClient(clien2);
carRental.AddClient(clien3);
Car car1 = new Car("1111", "Mercedes-Benz");
Car car2 = new Car("2222", "BMW");
Car car3 = new Car("3333", "Audi");
Car car4 = new Car("4444", "Ferrari");
carRental.AddCar(car1);
carRental.AddCar(car2);
carRental.AddCar(car3);
carRental.AddCar(car4);
}