True when Two Factor Authentication is required for this login. A One Time Password will be sent to the phone number on record for the user account. Make a subsiquent request to the /v1/Users/2FAKey endpoint with the One Time Password to complete Two Factor Authentication.
When the User account is setup for Device/Browser verification this field will contain a value. Send this value with subsequent requests to /v1/Users/LoginBrowser to remember 2FA verification requests.