The idle culler lives as a script in at least 3 different
places:

    In the JupyterHub repo, as an 'example'
    https://github.com/jupyterhub/jupyterhub/tree/d126baa443ad7d893be2ff4a70afe9ef5b8a4a1a/examples/cull-idle
    In the TLJH repo, as a core part of the service
    https://github.com/jupyterhub/the-littlest-jupyterhub/blob/01ba34857dd4e316d839034ae2b3cc400b929964/tljh/cull_idle_servers.py.
    This is an import from a specific version of the JupyterHub repo,
    and has had a couple of changes made to it since.
    In the z2jh repo, as a core part of the service
    https://github.com/jupyterhub/zero-to-jupyterhub-k8s/blob/c3f3be25f8ae6c72d02f385f41983b70ee1d416e/jupyterhub/files/hub/cull_idle_servers.py
    This is also an import from a specific version of the JupyterHub
    repo, but has had a lot more work done on it. Most had been sync'd
    back the JupyterHub repo, but some had not been. See
    https://github.com/jupyterhub/zero-to-jupyterhub-k8s/commits/9c15a42b1227f3b54826f273f1689e4dc8c8e12e/images/hub/cull_idle_servers.py
    and https://github.com/jupyterhub/zero-to-jupyterhub-k8s/commits/master/jupyterhub/files/hub/cull_idle_servers.py

The idle culler is a core integral part of every JupyterHub deployment
these days. It would be great if it was maintained separately on
its own, without being split across multiple repos.

The latest changes had been to the version in the JupyterHub repo, so I
copied it (while preserving commit history, because credit is important)
to a new repository: https://github.com/yuvipanda/jupyterhub-idle-culler

I looked through z2jh and tljh copies, and cherry-picked the following
changes manually

jupyterhub/zero-to-jupyterhub-k8s@ae80fb5
jupyterhub/zero-to-jupyterhub-k8s@836f19a
jupyterhub/zero-to-jupyterhub-k8s@a0787c6
jupyterhub/zero-to-jupyterhub-k8s@b230ef8
20374db#diff-f00cd100e9f673285208aaa6fc0c3212

There were a few from https://github.com/jupyterhub/zero-to-jupyterhub-k8s/commits/9c15a42b1227f3b54826f273f1689e4dc8c8e12e/images/hub/cull_idle_servers.py
I could not apply, but mostly because those features had been
re-implemented already.

Right now, the package is a direct port of the code we had. Once
this settles in, I am hopefull we can iterate faster and make cool
new changes.