title: Automapper - map to Interface type property without creating concrete class
body: <p>I want to be able to map to IFoo.IBar.Name <strong>without</strong> creating concrete object of type IBar myself.
  It's easy to do with proxy at CreateMap level: <code>Mapper.CreateMap&lt;Person, IFoo&gt;()</code>, but how to achieve it for custom inner interface type members ? </p>
  
  <pre><code>public class Test
  {
      [Fact]
      public void MapToInnerInterface()
      {
          const int id = 1;
          const string name = "Peter";
          var person = new Person {Id = id, Name = name};
  
          Mapper.CreateMap&lt;Person, IFoo&gt;()
              .ForMember(dest =&gt; dest.Bar.Name, c =&gt; c.MapFrom(src =&gt; src.Name));
  
          var mapResult = Mapper.Map&lt;IFoo&gt;(person);
  
          Assert.Equal(id, mapResult.Id);
          Assert.Equal(name, mapResult.Bar.Name);
      }
  }
  
  public interface IFoo
  {
      int Id { get; set; }
      IBar Bar { get; set; }
  }
  
  public interface IBar
  {
      string Name { get; set; }
  }
  
  public class Person
  {
      public int Id { get; set; }
      public string Name { get; set; }
  }
  </code></pre>