Add text (primer?) to discuss our stance on security

[duglin]

write-up some text about our thoughts around how security + CE should work, and why we don't really want to invent security mechanisms here - instead we leverage existing ones. E.g. via bindings (e.g. S/MIME)

was an old agenda AI

cc @clemensv

[github-actions]

This issue is stale because it has been open for 30 days with no
activity. Mark as fresh by updating e.g., adding the comment /remove-lifecycle stale.