add jinja templating

[ltalirz]

rough draft of how jinja templating could work.

missing: parsing of default values (perhaps not as easy as I thought)

[unkcpz]

Hi @ltalirz, I think this PR is a very important feature. We are going to send an email to THEOS group to ask people to test the newly released qe-app. If this can be done before sending it, we have more options with more accounts rather than hardcoded mr0 on eiger.cscs.
Let me know if you gonna finish this one, or do you mind if I push more commit here to try to finish this?

[unkcpz]

From my perspective, this templating feature by jinja is more about how we use this aiida-code-registry repository.
At the moment, it is only a repository to store computers and codes setup config files, and automatically generate a page for aiidalab.
If it is for aiidalab, the jinja can be easily converted there therefore we just need to have a database of templates rather than the config files that can be directly used in verdi. But this is a limited use case.

If we want to verdi computer setup <template>, we need to support it there or was your purpose in this PR to provide the cli in this package to setup resources?

[ltalirz]

Let me know if you gonna finish this one, or do you mind if I push more commit here to try to finish this?

Since this is time-critical, please go ahead and make the changes you need for your use case.

If we want to verdi computer setup <template>, we need to support it there or was your purpose in this PR to provide the cli in this package to setup resources?

Since setting up a new computational environment for yourself or a group of users is a recurring problem that currently has no satisfactory solution, over the last weeks I've been thinking bit about how to address it.
I already have some code and I will open a separate issue for it later today (and ping you there as well); don't let it slow you down.