boostrap v3 is EOL upstream; migrate to bootstrap v5

[juliangilbey]

This was reported as https://bugs.debian.org/1088418 and I quote from there.

Unfortunately, bootstrap versions 3 and 4 have been EOL'ed by upstream and it is difficult to provide security support for them.

Projects depending on the unmaintained bootstrap versions are encouraged to migrate to bootstrap v5 (src:bootstrap-html). Please note that bootstrap v5 is not just a drop-in replacement, and some work on the upstream side may be needed. Upstream provides these migration guides that may help:

https://getbootstrap.com/docs/4.6/migration/ (for migrating first from v3 to v4, which is also EOL, before the v4 to v5 migration)
https://getbootstrap.com/docs/5.3/migration/

Please, consider migrating to bootstrap v5.

Thank you!

[krassowski]

I agree this would be desirable as JupypterHub migrated to Bootstrap 5 not long ago (in JupyterHub v5). That said I would think the security implications are minimal as it seems jupyter-server only uses the CSS part of bootstrap and not any JS.