Single Sign-On (SSO) for Flex is now Generally Available. Flex SSO is used to login each user into the Flex UI and it handles the authentication and authorization of all requests from Flex to Twilio's APIs.
Breaking Change: We have now deprecated our original SSO Login URL (preview.twilio.com/iam), and on April 1, 2020 we will disable this URL. To continue using Flex, you must update your SSO configuration. Details on the required configuration changes are available in our migration guide.