den.namespace "namespace" sources is a v1 convenience function that creates a scoped aspect registry with external merge and flake re-export.
It takes a namespace name and a list of external sources (flakes with a denful.<namespace>.* attrpath),
merges their aspect content with any locally-declared content under the same namespace,
and re-exports the result under config.flake.denful.<namespace>.
The sources argument accepts: