title: fluent nhibernate many to many convention automapping
body: <p>I am using FluentNH with automapping and conventions. I set up a Many-to-Many convention as such:</p>
  
  <pre><code>    public class HasManyToManyConvention : IHasManyToManyConvention
      {
          public void Apply(IManyToManyCollectionInstance instance)
          {
              instance.Key.Column(instance.EntityType.Name + "Id");
              instance.Relationship.Column(instance.Relationship.StringIdentifierForModel + "Id");
          }
      } 
  </code></pre>
  
  <p>Assuming these are my tables:
          User(Id,Username,Password), 
          Role(Id,Name)</p>
  
  <p>Upon database generation, the associative table is being generated fine: 
          UserInRole(UserId,RoleId)</p>
  
  <p>However, it has no composite primary key set. Any idea how to fix this from the convention?</p>
  
  <p>Anyone? Might it be this is currently not supported by Fluent?</p>