Create a better Custom Packages component?

[dometto]

The current SURF Custom Packages component has a number of downsides:

• it requires a URL to a requirements file, so you cannot leave the parameter empty in the portal if you don't want to have any custom packages in your catalog item or workspace. (I think it would be nice to add the option for custom packages to e.g. our Python Workbench catalog item.)
• it installs miniconda, but we have our own miniconda component that is more versatile. It would be better if the Custom Packages plugin simply checked if miniconda is pre-installed, and throws a warning if not.
• it only supports installing custom packages systemwide, while our python-workbench, miniconda, and anaconda components support installing these package managers in userspace. Perhaps it would be nice if the custom packages component could install packages on a per-user basis, too?
• it only supports installing pip packages via miniconda. Is that enough, or would we like to support custom packages for pip as well?
• other package managers: e.g. mamba, poetry?

[dometto]

We could ask SURF to do this but I think we may be better off creating it ourselves. But f I'm going to work on this it would be great to know exactly what we want. :) @chStaiger @jelletreep could you let me know what you think about the features mentioned above?

[jelletreep]

Interestingly Surf has used Mamba in custom packages earlier 😄

What I find really annoying when using the custom packages component, is that it is complicated to install additional packages to the existing kernel. one has to run conda init, restart the terminal, clone the environment, activate the cloned environment and then conda install a new package. I would say that it should be possible to reduce this to only activating the environment and then installing a package?

Poetry is a nice to have, but I think conda is at the moment by far the most popular, i haven't seen use cases for poetry at the moment.
pip installs via conda do a regular pip install if I am correct, so I don't think there has to be something separate for pip