In order to migrate users, we need to stop proliferation of DataBroker as a unified access which can span multiple datastores in a single transaction.

Rather than migrating users in one go to a new API, expose two facades with odl:type={config,oper}, each of which will be bound a specific datastore and will reject attempts to access any other datastore. This should work dynamically, based on the odl:type=default databroker currently injected.

We then can migrate users to use a specific databroker (or separate instances) and once that is done, we can start switching them to a more specific interface.