Build and publish Docker Hub image for amd64 and arm64

[manics]

Z2JH requires the Docker image from this repo:
https://github.com/jupyterhub/zero-to-jupyterhub-k8s/blob/08faa6f197e478ca28ce23d083287d37096cbb36/jupyterhub/values.yaml#L191

This PR modifies the npm-publish.yml GitHub workflow to also build the Docker image using Docker buildx for linux/amd64 and linux/arm64. The large diff is due to me renaming npm-publish.yml to publish.yml, the individual commit diffs are clearer. As we've done with other repos I've followed the policy of always running the publish workflow steps for all pushes, with only the actual push/publish step guarded by the tag conditional.

This requires the following Docker Hub secrets:

• {{ secrets.DOCKERHUB_USERNAME }}
• {{ secrets.DOCKERHUB_TOKEN }}

I presume the image is currently built using a Docker Hub automated build, so that will need to be disabled before this is merged (EDIT: done). An additional advantage of doing the build/push in a GitHub workflow instead of with the automated Docker Hub build is that we can easily push to other registries in future.

This uses a new action manics/action-major-minor-tag-calculator (currently in an intermediate GitHub org for various boring reasons but it could probably move to JupyterHub if there's agreement 😄) to generate the tags needed for the Docker image from the GitHub tag. E.g. 1.2.3 is expanded to Docker tags [1.2.3, 1.2, 1, latest] unless this is a backported tag in which case the newer tags aren't updated.

[consideRatio]

Excellent to have you working on this @manics !! ❤️

[consideRatio]

Thanks for the comments!

I've...

• added the DOCKERHUB_USERNAME and DOCKERHUB_TOKEN and made our bot account have a dedicated access token for this repo
• given the bot account read/write permissions to the image named jupyterhub/configurable-http-proxy
• disabled the hub.docker.com's autobuild functionality so that we will rely on this workflow to do the job for us

[consideRatio]

I'd personally be happy to introduce the GitHub action to calculate the tags to the jupyterhub org btw. @minrk perhaps you can comment on that as well?

• Action point: take a decision to move the action to jupyterhub org or not

I suggest we release CHP 4.4.0 when this is included as well, we have since current 4.3.1 bumped some npm production level dependencies, and i consider this a non-breaking enhancement to associate with a new version motivating a minor version bump.

• Action point: reach agreement to cut a version: 4.3.2 decided!

[consideRatio]

Lgtm!

[minrk]

👍 great! Also happy to trigger a release just for the CI, though I think 4.3.2 is appropriate, as there are no user-facing changes since 4.3.1.

[consideRatio]

@manics I consider this ready for merge at this point then! Go for a self-merge if you think it's ready as well!

[manics]

Let me see if I can move the action to jupyterhub first....

[consideRatio]

@manics nice deal! I'll make a changelog and cut a release once we merge this

[welcome]

Congrats on your first merged pull request in this project! 🎉

Thank you for contributing, we are very proud of you! ❤️

[consideRatio]

Beuatiful!!!