def add_association_columns(association, *columns)
      column = self[association]
      raise ArgumentError, "unknown column #{association}" if column.nil?
      raise ArgumentError, "column #{association} is not an association" if column.association.nil?
      raise ArugmentError, "column #{association} is not singular association" unless column.association.singular?
      raise ArugmentError, "column #{association} is polymorphic association" if column.association.polymorphic?

      klass = column.association.klass
      columns.each do |col|
        next if find_by_name col
        @set << ActiveScaffold::DataStructures::Column.new(col, klass, column.association)
      end
    end
def add_association_columns(association, *columns)
      column = self[association]
      raise ArgumentError, "unknown column #{association}" if column.nil?
      raise ArgumentError, "column #{association} is not an association" if column.association.nil?
      raise ArugmentError, "column #{association} is not singular association" unless column.association.singular?
      raise ArugmentError, "column #{association} is polymorphic association" if column.association.polymorphic?

      klass = column.association.klass
      columns.each do |col|
        next if find_by_name col
        @set << ActiveScaffold::DataStructures::Column.new(col, klass, column.association)
      end
    end
add columns from association (belongs_to or has_one)
 these columns will use label translation from association model
 they will be excluded, so won't be included in action columns
 association columns will work for read actions only, not in form actions (create, update, subform)