gh-37246: minor details in modular
namely
- use ruff to fix some containement tests
- add links to some error codes in the doc
- plus some http to https
### :memo: Checklist
- [x] The title is concise, informative, and self-explanatory.
- [x] The description explains in detail what this PR is about.
URL: https://github.com/sagemath/sage/pull/37246
Reported by: Frédéric Chapoton
Reviewer(s): Matthias Köppe
