title: Missing Mapping Model after Adapting to another model
body: <p>I have 2 service models and 2 DAL models. While creating new Author, I want to save its books to Book table. So, I send payload as json. However, If I try to adapt model to Book model, its values are null.So I can solve this problem. I also tried <code>model.Adapt&lt;IEnumerable&lt;Book&gt;&gt;()</code>, this also comes null.</p>
  
  <pre><code>public async Task&lt;AuthorRequest&gt; CreateAsync(AuthorRequest model)
  {
      var authorEntity= model.Adapt&lt;Author&gt;(); // works fine
      var bookEntity =model.Adapt&lt;Book&gt;();//null
  }
  </code></pre>
  
  <p><strong>Service.Models</strong></p>
  
  <pre><code>public class AuthorRequest :Identifiable&lt;string&gt;
  {
      public string override Id{get;set;}
  
      [Attr("name")]
      public string Name { get; set; }
  
      [Attr("surname")]
      public string Surname { get; set; }
  
      public  ICollection&lt;BookRequest&gt; Books{get; set; }
  }
  
  public class BookRequest :Identifiable&lt;string&gt;
  {
      public string override Id{get;set;}
      public string Title { get; set; }
  }
  </code></pre>
  
  <p><strong>DAL.Model</strong></p>
  
  <pre><code>public class Author : AuditableEntity
  {
      [JsonProperty("name")]
      public string Name { get; set; }
  
      [JsonProperty("surname")]
      public string Surname { get; set; }
  
      [JsonProperty("books")]
      public Relationship&lt;IList&lt;Book&gt;&gt; Books;
  }
  
  public class Book :AuditableEntity
  {
      [JsonProperty("Title")]
      public string Title { get; set; }
  
      [JsonProperty("Author")]
      public Relationship&lt;IList&lt;Author&gt;&gt; Author;
  }
  </code></pre>
  
  <p><strong>Mappings with mapster</strong></p>
  
  <pre><code>TypeAdapterConfig&lt;DAL.Models.Author, Service.Models.AuthorRequest&gt;.NewConfig();
  TypeAdapterConfig&lt;DAL.Models.Book, Service.Models.AuthorRequest&gt;.NewConfig();
  TypeAdapterConfig&lt;DAL.Models.Book, Service.Models.BookRequest&gt;.NewConfig();
  
  TypeAdapterConfig&lt;Service.Models.AuthorRequest, DAL.Models.Author&gt;.NewConfig();
  TypeAdapterConfig&lt;Service.Models.AuthorRequest, DAL.Models.Book&gt;.NewConfig();
  TypeAdapterConfig&lt;Service.Models.BookRequest, DAL.Models.Book&gt;.NewConfig();
  </code></pre>
  
  <p><strong>AuthorRequest.JSON</strong></p>
  
  <pre><code>{
      "name": "William",
      "surname": "Shakespeare",
      "books": [{
          "title": "Macheth"
      }]
  }
  </code></pre>