identify useful tests

not sure what to do here, except i know there are a lot of checks we can do, related to 1) preventing the book build from breaking and 2) checking our own style and formatting rules

• current test is slow - maybe there is a way to optimize?
• small checks when members push to a branch, to help identify possible issues when merging to main earlier?

changed milestone to %Backend book support: Phase 1

added IT label

will probably include a manual check once per year that all notebooks function with under new requirements.txt (Mattermost discussion)