Explore options for / usability when running proxying registries

[ableuler]

Some organizations use tools like https://jfrog.com/artifactory/ as proxy in front of public package/image repositories such as dockerhub, pypi, npm, etc. In this issue, it should be checked to what extent this complicates the RenkuLab deployment process or reduces the usability of the platform once deployed (eg pip installs inside interactive sessions might fail). Finally, as part of this issue we want to explore what options there are for mitigating the above problems and how those are best integrated in RenkuLab deployments.

[MichaelAML]

This feature has especially an impact in the build process of the Docker images for the interactive sessions. Inparticular it should be possible to use an alternative artifactory while building the image (i.e. installing the packages from requirements.txt, see for example here), but also during the actual interactive session when a user is installing further packages.

In case of Python (JupyterLab) it should be enough to configure pip to use alternatice PyPi repository via pip.conf (see here as well as conda via .condarc (see here).

In case of R (RStudio) it should be enough to configure RProfile.site to use an alternative CRAN repository (see here).