Authenticate the challenge ID (generated with /MFAChallenge.json) and token that was sent to your mobile device registered with BILL. In response, an mfaId value is generated and your API session is MFA trusted.
By default, MFA expires when the API session expires after 35 minutes of inactivity. If you set rememberMe as true in your /MFAAuthenticate.json request, the mfaId value is marked as trusted for 30 days. You can check the MFA status with /MFAStatus.json.