Function valid_namespace 

pub fn valid_namespace(name: &str) -> bool

A valid namespace name: 1–NS_MAX_LEN characters of [A-Za-z0-9_.-].

Deliberately narrower than a key: a namespace is an administrative label that appears in roles.json, in a rule definition and in stats, so it stays spellable without quoting. / is excluded on purpose — keys already contain it (ingest-git keys files on their repository path) and a namespace must never read as a key prefix.