Change database for migrating hosts

Below is our current database schema:

In this structure, it is impossible to recognize which Kea daemon holds a specific IP or hostname reservation. So, we don't know on which Kea daemon perform the migration.

I want to make the below changes:

• Replace the ip_reservation table's reference to host table with reference to local_host.
• Move the hostname column from host to local_host table
• (Optionally) Add a single-column primary key to the local_host table and add a unique index on the host_id, data_source, and daemon_id to preserve the existing constraints.