The adopted node still runs the predecessor's mongo container, and it must
keep running: invoicing points at novox.be:27017 and is not migrating in
this window. A module container named 'mongo' would be held at assign and
would replace the predecessor at take, cutting invoicing off its database.
The mesh's server coexists instead — fresh data directory, its own name,
auto-allocated machine port — and the predecessor retires with its last
consumer.