title: Is it possible add extra field in Sequelize relation?
body: <p>I have <code>belongsTo</code> relation like this:</p>
  
  <pre><code>classMethods: {
      associate: function(models) {
          User.belongsTo(models.Prefs, {timestamps: false, foreignKey: 'Type', targetKey: 'UserType'})
  
      }
  }
  </code></pre>
  
  <p>which produces </p>
  
  <pre><code> LEFT OUTER JOIN `prefs` AS `Prefs` ON `User`.`Type` = `Prefs`.`UserType`
  </code></pre>
  
  <p>The problem is that I also need to add extra check like </p>
  
  <pre><code>AND `Prefs`.`Section` = 'GLOBAL'
  </code></pre>
  
  <p>Is it possible?</p>