Re-enable custom HTTPS in the new AiiDA 2.x image

[danielhollas]

There is nothing to do on the image side. We need to connect to the certifcate via volumes (already possible with aiidalab-launch) and pass certain jupyter configuration when launching the container. This needs extra support in aiidalab-launch, as described in aiidalab/aiidalab-launch#155

https://jupyter-docker-stacks.readthedocs.io/en/latest/using/common.html#ssl-certificates

[danielhollas]

The current solution is to autogenerate self-signed certificates directly in the container by specifying GEN_CERT=yes in the Dockerfile per https://jupyter-docker-stacks.readthedocs.io/en/latest/using/common.html#additional-runtime-configurations

Later we want to be able to have custom certificates mounted via volume, though we need to solve the permission issue in that case.