add HasVogenConversion for nullable PropertyBuilder<TValueObject>

[apphost]

add HasVogenConversion for nullable PropertyBuilder
add HasVogenConversion for ComplexTypePropertyBuilder

#873

[SteveDunn]

Hi, thanks for the PR. I'll try to help get it working soon, sorry for the slow feedback, I get very little time for Vogen recently

[SteveDunn]

This isn't considered an overload in C#, hence the compiler errors.

[aminmashayekhi]

i add this Extension for handle this... is it ok?

public static class VogenEfExtensions
{
    public static PropertyBuilder<T?> HasVogenConversion<T>(this PropertyBuilder<T?> builder)
        where T : struct
    {
        var type = typeof(T);
        var fromMethod = type.GetMethod("From", BindingFlags.Public | BindingFlags.Static)
                         ?? throw new InvalidOperationException($"{type.FullName} does not have a public static From method.");
        var valueProp = type.GetProperty("Value", BindingFlags.Public | BindingFlags.Instance)
                        ?? throw new InvalidOperationException($"{type.FullName} does not have a public instance Value property.");

        var converter = new ValueConverter<T?, object?>(
            model => model == null ? null : valueProp.GetValue(model.Value),
            provider => provider == null ? (T?)null : (T)fromMethod.Invoke(null, new[] { provider })
        );

        return builder.HasConversion(converter);
    }

    public static PropertyBuilder<T> HasVogenConversion<T>(this PropertyBuilder<T> builder)
        where T : struct
    {
        var type = typeof(T);
        var fromMethod = type.GetMethod("From", BindingFlags.Public | BindingFlags.Static)
                         ?? throw new InvalidOperationException($"{type.FullName} does not have a public static From method.");
        var valueProp = type.GetProperty("Value", BindingFlags.Public | BindingFlags.Instance)
                        ?? throw new InvalidOperationException($"{type.FullName} does not have a public instance Value property.");

        var converter = new ValueConverter<T, object?>(
            model => valueProp.GetValue(model),
            provider => (T)fromMethod.Invoke(null, new[] { provider })
        );

        return builder.HasConversion(converter);
    }
}