Allow object definitions to reference other objects

Is there an example how to use the input bindings to retrieve related objects?

Like I would like to retrieve something like this (retrieve `A` through an input binding)

```
public class A {
public int Id {get; set;}
public int BId {get; set;}
public virtual B BObject {get; set;}
}

public class B {
public int Id {get; set;}
}
```

The issue names no file, test, or entry point. Start by locating the SQL input-binding implementation and existing object-definition examples, then clarify whether navigating from A to BObject is supported. Done should mean a documented and tested way to retrieve related objects through an input binding, or a clear statement of the limitation.

Written by the indexing model from the issue text.