Import multiple bind9 zone files

A common use case for a migration is importing a new tenants often complicated DNS configuration. To aide in the process, admins and tenants would benefit from the capability to import multiple bind9 zone files in one request.

An acceptable solution could be a command line client that takes a directory of zone files as a parameter.

Other details:
1. Ideally, the import can happen in one transaction. For the sake of progress, this blueprint can be split to cover the transactional aspect.
2. This blueprint depends on the abillity to import a single zone file.
3. What happens if a zone is imported that overwrites a zone currently managed in the system?