/// <summary>
 /// Return a C# nullable type.
 /// The function return an 'object' type if the given model type is null (void).
 /// </summary>
 /// <param name="v"></param>
 /// <returns></returns>
 public static string AsNullableTypeOrDefault(this IModelType v)
 => v == null ? "object" : v.AsNullableType();