Delete a namespace

Deletes an empty namespace. A namespace that still holds anything conflicts, and the error counts what remains: mailboxes, API keys, webhook endpoints filtered to it, domains, senders, contacts, or template projects. Delete each, or return it to organization level with DELETE /v1/namespaces/{id}/resources/{type}/{resourceId}; mailboxes, keys, and webhook endpoints cannot move and are deleted. Messages keep the namespace they ran in.