Support RADIUS protocol for 2FA / OTP

Problem to solve

Customers in secure environments may be required to use the RADIUS protocol to obtain a one-time passcode. GitLab does not currently support this option.

Target audience

Product Manager

Proposal

Support RADIUS as an additional OTP protocol

What does success look like, and how can we measure that?

Customers who rely on RADIUS are able to integrate it into GitLab

Links / references

ZenDesk ticket # 112269 (internal link)

/cc @jeremy