instance method authenticated?

# File actionmailbox/app/controllers/action_mailbox/ingresses/mailgun/inbound_emails_controller.rb, line 64
      def authenticated?
        if key.present?
          Authenticator.new(
            key:       key,
            timestamp: params.require(:timestamp),
            token:     params.require(:token),
            signature: params.require(:signature)
          ).authenticated?
        else
          raise ArgumentError, <<~MESSAGE.squish
            Missing required Mailgun Signing key. Set action_mailbox.mailgun_signing_key in your application's
            encrypted credentials or provide the MAILGUN_INGRESS_SIGNING_KEY environment variable.
          MESSAGE
        end
      end