❔ ✅ custom mapper and resolvers

public static class MappingExtensions
{
    public static PublicAd MapToPublicAd(this Ad ad, User user)
    {
        return new PublicAd
        {
            Claimed = ad.Claimed,
            Distance = // I don't know
        };
    }
...

public class DistanceResolver
{
    private readonly IDistanceService _distanceService;

    public DistanceResolver(IDistanceService distanceService)
    {
        _distanceService = distanceService;
    }

    public double Resolve(Ad ad, User user)
    {
        if (user is null)
        {
            throw new ArgumentException($"No valid user passed to");
        }

        if (user.Municipality is null || source.Municipality is null)
        {
            return -1d;
        }

        return _distanceService.GetDistanceInKm(
            ad.Municipality.Location!.Y, 
            ad.Municipality.Location!.X,
            user.Municipality.Location!.Y,   
            user.Municipality.Location!.X
        );
    }
}