Document how to find the current instance configuration

From @aqualls in !126018 (comment 1467665617)

I think we should spin off an issue to document how to find the current instance configuration. I grepped for SSH fingerprints in the docs and didn't find anything. That phrase would've been used in the instructions for users to find the current instance configuration link, which tells me the destination page is probably an easter egg.

doc/user/ssh.md is a plausible spot, but it might not be right. That would go to the TW for ~"group::authentication and authorization", Jon Glassman. Documenting the CI/CD limits, for example, might need to go to Marcel Amirault.

tl;dr a follow-up seems a safe bet!