errfactory.rb

class ApiError < StandardError
  def self.build(status:, message:, key:)
    Class.new(self) do
      define_method(:status) { status }
      define_method(:message) { message }
      define_method(:key) { key }
    end
  end
end

e = ApiError.build(status: 400, message: "X", key: :lol)
e.class

raise e # => errfactory.rb:14:in `<main>': X