title: Bi-directional association query question: How do you query an owned class's owner using GORM?
body: <p>Say you have two domain classes: Authors and Books. Authors can have many Books, but a Book can only have one Author.</p>
  
  <pre><code>class Author {
    static hasMany = [Book]
  }
  
  class Book {
    static belongsTo = Author
  }
  </code></pre>
  
  <p>How do you query is book's author? </p>
  
  <p>This doesn't seem to work:</p>
  
  <pre><code>def book = Book.get(1)
  book.author 
  </code></pre>