instance method deprecation_removal_warning

# File activemodel/lib/active_model/errors.rb, line 585
      def deprecation_removal_warning(method_name, alternative_message = nil)
        message = +"ActiveModel::Errors##{method_name} is deprecated and will be removed in Rails 7.0."
        if alternative_message
          message << "\n\nTo achieve the same use:\n\n  "
          message << alternative_message
        end
        ActiveSupport::Deprecation.warn(message)
      end