add_timestamps_for_alter

# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1820
        def add_timestamps_for_alter(table_name, **options)
          options[:null] = false if options[:null].nil?

          if !options.key?(:precision) && supports_datetime_with_precision?
            options[:precision] = 6
          end

          [
            add_column_for_alter(table_name, :created_at, :datetime, **options),
            add_column_for_alter(table_name, :updated_at, :datetime, **options)
          ]
        end