title: Sequelize Join on Non Primary Key
body: <p>I have two tables I need to associate. TableA has One TableB. I'm able to do this in the TableA Model:</p>
  
  <pre><code>TableA.hasOne( models.TableB, { as: 'TableB', foreignKey: 'someID' } );
  </code></pre>
  
  <p>Looking at the SQL, this tries to join TableA.ID and TableB.someID. What I actually want, is to join TableA.someNonPrimaryKey and TableB.someID. </p>
  
  <p>How can I tell sequelize to join with someNonPrimaryKey?</p>