title: one to one relationship with columns that are not id
body: <p>I have BudgetLine model. The model has budget_item_id column.</p>
  
  <p>Second model is BudgetItem. it has an id and a column: full_name.</p>
  
  <p>Now, I want to call: budget_line.item_name and get the name that is corresponding to the full_name in BudgetItem.</p>
  
  <p>I tried (in BudgetLine):</p>
  
  <pre><code>has_one :item_name, :class_name =&gt; 'BudgetItem', :foreign_key =&gt; 'budget_item_id'
  </code></pre>
  
  <p>But it is not working.</p>