MFA Admin Documentation

[lomky]

Thanks for creating an issue! Please fill out this form so we can be sure to have all the information we need, and to minimize back and forth.

• What are we trying to do?

• Capture the info from the #2819 PR into our documentation

• What feature or behavior is this required for?
  Future us understanding!

• How could we solve this issue? (Not knowing is okay!)

• Add a section to SECURITY.md - maybe elsewhere too.
• Maybe its own small doc too with a high level overview in the ADMIN section?

• Anything else?
  Nope!