mastercontainer - use Caddy for generating self-singed cert

[szaimen]

Alternative approach to #3069
Supercedes #3069

[szaimen]

@Zoey2936 would this approach be fine for you?

[Zoey2936]

@Zoey2936 would this approach be fine for you?

what is different to #3096?

[szaimen]

@Zoey2936 would this approach be fine for you?

what is different to #3096?

Mainly separating the change to caddy from moving to a full-blown apache conf which is better to test

[szaimen]

Thanks :)

[szaimen]

I fear this does not work. I get the following issue:

automation policy from site block is also default/catch-all policy because of key without hostname, and the two are in conflict: []certmagic.Issuer{(*caddytls.InternalIssuer)(0xc00032c360)} != []certmagic.Issuer{(*caddytls.ACMEIssuer)(0xc0003fce00)}

So reverting.