ssh validation error should have more information

[jsoref]

Summary

Provide details about what ssh connection failed and make it easier to act on this information

Motivation

When #7723 happened, we got some very unhelpful messages:

rpc error: code = Unknown desc = ssh: handshake failed: knownhosts: key mismatch argocd

TYPE	NAME	REPOSITORY	CONNECTION STATUS	...
git		git@github.com:...	❌ Failed	⋮
git		git@github.com:...	❌ Failed	⋮
helm	argo	https://argoproj.github.io/argo-helm	✅ Successful	⋮

SERVER NAME	CERT TYPE	CERT INFO	...
bitbucket.org	ssh ssh-rsa	SHA256:zzXQOXSRBEiUtuE8AikJYKwbHaxvSc0ojez9YXaGp1A	⋮
github.com	ssh ssh-rsa	SHA256:nThbg6kXUpJWGl7E1IGOCspRomTxdCARLviKw6E5SY8	⋮
gitlab.com	ssh ecdsa-sha2-nistp256	SHA256:HbW3g8zUjNSksFbqTiUWPWg2Bq1x8xdGUrliXFzSnUw	⋮
gitlab.com	ssh ssh-ed25519	SHA256:eUXGGm1YGsMAS7vkcx6JOJdOGHPem5gQp4taiCfCLB8	⋮
gitlab.com	ssh ssh-rsa	SHA256:ROQFvPThGrW4RuWLoL9tq9I9zJ42fK4XywyRtbOz/EQ	⋮
ssh.dev.azure.com	ssh ssh-rsa	SHA256:ohD8VZEXGWo6Ez8GSEJQ9WpafgLFsOfLOtGGQCQo6Og	⋮
vs-ssh.visualstudio.com	ssh ssh-rsa	SHA256:ohD8VZEXGWo6Ez8GSEJQ9WpafgLFsOfLOtGGQCQo6Og	⋮

Proposal

• The ssh: handshake failed error should report:
  1. destination host
  2. expected keys
  3. received keys
• Everything that links to that error state should include that information
• The App view for this error should link back to the /settings/repos page
• Repositories on the Repositories page should link to the /settings/certs page

[jannfis]

I agree that we must improve error reporting (and not only in this special place).

However, for some of the information we rely on third-party libraries (e.g. go-git and x/crypto/ssh) to provide us with the the details. Emitting the host name in the error message should be a quick fix, but getting details about the expected and received key material is something that we probably cannot solve in Argo CD code. I'd be glad if someone proves me wrong, tho :)

[jsoref]

I'll take whatever incremental bits I can get. For the rest, if people could file issues and cross link, that'd be great. I didn't have enough information from the error to even know where to file the rest of the bug 😦 .

[alexmt]

Fixed by #7722 . The fix is available in v2.1.7 release

[jsoref]

Err, this is not about the fact that github isn't working, it's about the error reporting for when any ssh server isn't working.