Updates needed for Caddy

[gene1wood]

@francislavoie made some good suggestions in #153

I'm copying them here so we can consider them and potentially PR some changes based on them

@francislavoie writes

Caddy v2 doesn't support lower than TLS 1.2 at all (because older TLS versions are completely broken). So all those clients won't work.

IMO the "old" option for Caddy should be totally disabled. The intermediate option should remove all tls config (irrelevant) and turning off TLS 1.2 with "modern" is kinda silly and counterproductive, so I'd also just remove the tls config for that option as well.

Caddy's defaults are secure, there's no reason to tune cipher suites, and configuring cipher suites has no effect at all when using TLS 1.3 because the Go stdlib automatically ordering them. See https://go.dev/blog/tls-cipher-suites as I mentioned earlier.

Also, Caddy doesn't use OpenSSL, the website makes it seem like it uses it by showing the OpenSSL version on the right. And Caddy v2.1.1 is a long-since EOL version.

Caddy v1 is no longer supported, so it does not make sense at all to continue showing config for it. Don't recommend config for EOL software, please.