def bitmask_scopes(bitmask)
      send("values_for_#{bitmask}").each do |value|
        scope value, send("with_#{bitmask}", value)
        scope "not_#{value}", send("without_#{bitmask}", value)
      end
    end
def bitmask_scopes(bitmask)
      send("values_for_#{bitmask}").each do |value|
        scope value, send("with_#{bitmask}", value)
        scope "not_#{value}", send("without_#{bitmask}", value)
      end
    end
Setup scopes for Bitmask attributes

 Scopes are setup with the same name as the value, and include both
 .value and .not_value versions
 @arg [Symbol] bitmask the name of the bitmask attribute