Add demo repositories mechanism to populate user's space

[viniciusdc]

Reference Issues or PRs

closes #2179

What does this implement/fix?

This PR exposes/introduces a new way to easily instantiate GitHub repositories in the user superlab pod during launch time. This helps streamline demos, examples, and other data that the administrator considers needed for any user who starts using the platform.

Description

The primary goal of this PR is to streamline the initialization and distribution of the Git repositories when a user first launches its JupyterLab instance. The main addition is simplifying the script's command-line arguments to make it easier to use within a Kubernetes context.

In the nebari-config.yaml side, a new field was included (optional) to distribute the location where the given repository will be cloned into (relative to the user /home directory) and its URL.
block syntax

jupyterlab:
  initial_repositories:
    - <path/to/folder>: <github/repository/url>
    - <path/to/folder/or/subfolder>: <github/repository/url>
    - ...

Put a x in the boxes that apply

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds a feature)
• Breaking change (fix or feature that would cause existing features not to work as expected)
• Documentation Update
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no API changes)
• Build related changes
• Other (please describe):

Testing

• Did you test the pull request locally?
• Did you add new tests?

Any other comments?

[viniciusdc]

Currently fixing an issue with permissions when executing the script, will commit the update in a few minutes once that's fixed

[viniciusdc]

Fixed, now I will rename the yaml config field based on the suggestions given on the issue

[viniciusdc]

I've done some testing already, but now I will check with the examples we discussed during the last meeting

[viniciusdc]

Here are some tests by specifying the following in the nebari-config.yaml:

jupyterlab:
  initial_repositories:
    - examples/nebari-demo: https://github.com/nebari-dev/nebari-demo.git
    - examples/big-data: https://github.com/nebari-dev/big-data-tutorial-90min.git

Screenshot from the initContainer running the clone:

Image from the jupyterlab user pod:

** Permission given to any git repository created by this method will always be 1000:100, which as of now, always maps to <current-user:<users-group>>

When the pod is restarted, the script does not run again if the git repos already exists: