Due to a bug introduced in `df8e4e6c88a8bfb6c1ec6b07dcda64093b477cbe`, IPv6
addresses in the configuration file might have ended up in the database
tagged with `type = "dns"`, which is incorrect. The bug was fixed in
`a2e72b48e79d090d33f6c13c485239947de0522e`.
However, Radicle 1.7.0 was released in between those two versions, so a
this migration to repair the entries is added.
Tests are added in `test::migration_8` module. This requires some test
setup, mainly a `Database::memory_up_to_migration` constructor that is only
available to test code.
a6a3716f5d