Malfunction with a jupyterhub-singleuser startup influencing xsrf checks

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I've concluded that the current images in :main image doesn't work when started with jupyterhub-singleuser 4.1.3.

It doesn't matter if jupyterhub 4.0.2 etc is used on the server side - this is user environment side stuff where the jupyter server starts rejecting things.

I've tested to conclude that if jupyterhub-singleuser 4.1.0-4.1.3 is used in the user environment, we error, but if 4.0.2 or 4.1.4 is used we are OK and things work. So, this can be closed once we can publish an image that will use jupyterhub 4.1.4. I've triggered a rebuild of jupyter/docker-stacks to get 4.1.4 jupyterhub released today in a base-notebook image.

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Verified to now be resolved with latest main images.