Allow customer SSL cert on https_port directive

[thscheer]

Running the latest squid docker image, I tried to use a custom server.key / server.cert for using https with

https_port 8128 cert=/etc/squid/ssl/server.crt key=/etc/squid/ssl/server.key

I tried several options like acel / transparent / intercept aso. but never got a working configuration.
Which is the correct option to work with the docker/squid ?