__joinedColumns__(joinName, shortAlias) {
    let relationship = this.Model.relationships().findExplicit(joinName);
    return relationship.getModel().columnQueryInfo().map(column => {
      column.identifier = shortAlias;
      column.table = relationship.getModel().table();
      column.alias = `\$${joinName}\$${column.name}`;
      column.shortAlias = `\$${shortAlias}\$${column.name}`;
      column.joined = true;
      return column;
    });
  }
Retrieve all joined column data for a given join
@param {string} joinName The name of the join relationship
@param {string} shortAlias The shortened name of the join relationship
@private