Support for custom certificates in TLS handler

[rcm-25]

It would be nice to have the option to configure custom certificates for the L4 TLS handler via the Caddyfile as it is possible in Caddy with the tls <cert_file> <key_file> directive.

I would e.g. like to use it like this (in the context of docker compose):

{
    layer4 {
        127.0.0.1:8883 {
            route {
                tls my_cert.crt my_cert.key
                proxy <docker_container>:1883
            }
        }
    }
}

This feature request emerged from the discussion in Custom certificates for TLS termination in layer4 app

[mholt]

Good idea, (sort of, lol) -- we like automation around these parts. Why do you need manually-managed certs?

[rcm-25]

In my use case, I use Caddy with the Layer4 module as a reverse proxy in an environment that may not have online access.
I would therefore like to be able to specify my own certificate here.