class ActionMailbox::Ingresses::Mailgun::InboundEmailsController

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 API key. Set action_mailbox.mailgun_api_key in your application's
      encrypted credentials or provide the MAILGUN_INGRESS_API_KEY environment variable.
    MESSAGE
  end
end