title: How to update related entities using GraphDiff?
body: <p>I have the following model:</p>
  
  <pre><code>public class Customer
  {
      public int Id {get; set;}
      public string Name {get; set;}
      public int AddressId {get; set;}
      public virtual Address Address {get; set;}
      public virtual ICollection&lt;CustomerCategory&gt; Categories {get; set;}
  }
  
  public class CustomerCategory
  {
      public int Id {get; set;}
      public int CustomerId {get; set;}
      public int CategoryId {get; set;}
      public virtual Category Category {get; set;}
  }
  
  public class Address
  {
      public int Id {get; set;}
      public string Street{get; set;}
      public virtual PostCode PostCode {get; set;}
  }
  </code></pre>
  
  <p>From the above, and using GraphDiff, I want to update the customer aggregate as follows:</p>
  
  <pre><code>dbContext.UpdateGraph&lt;Customer&gt;(entity, 
              map =&gt; map.AssociatedEntity(x =&gt; x.Address)
                        .OwnedCollection(x =&gt; x.Categories, with =&gt; with.AssociatedEntity(x =&gt; x.Category)));
  </code></pre>
  
  <p>But the above is not updating anything!!</p>
  
  <p>What is the correct way to use GraphDiff in this case?</p>