title: How to create a two foreign key relation in Objection.js
body: <p>Is there any way to create a two foreign key relation in Objection.js. Something like following:</p>
  
  <pre><code>  static get relationMappings() {
      return {
        childs: {
          relation: Model.HasManyRelation,
          modelClass: childModel,
          join: {
            from: 'parent.id',
            to: 'child.parent_id'
          },
          join: { // Another foreign key
            from: 'parent.record_id',
            to: 'child.parent_record_id'
          }
        }
      }
    }
  </code></pre>