Inject custom certificates into images

[MoritzWeber0]

Some corporates use their own CAs to access other services in the company. Accessing other services is esp. essential for the Jupyter image, where it's common to send requests to other internal services.

But it's also interesting for the Capella image, where the Git server may require a custom certificate.

We should support the injection of custom certificates during build- or runtime.

During build time, it can be copied via a COPY instruction in the base image (has to be adjusted in the CI templates as well).
During runtime, the certificates could be mounted to a directory.

To make Python understand the certificates, add the following line to the Dockerfile:

RUN pip install certifi && cat /etc/ssl/certs/*.pem > "$(python -m certifi)"