private Dealer AddDealer(JsonCar car)
        {
            var cityToAdd = this.databaseContext.Cities.FirstOrDefault(city => city.Name.Equals(car.Dealer.City))
                            ?? new City { Name = car.Dealer.City };

            return new Dealer { Name = car.Dealer.Name, City = cityToAdd };
        }
 private Manufacturer AddManufacturer(JsonCar car)
 {
     return this.databaseContext.Manufacturers.FirstOrDefault(man => man.Name.Equals(car.ManufacturerName))
            ?? new Manufacturer { Name = car.ManufacturerName };
 }