db: Add last_sync_at, next_sync_at and namespace_user_id
Created by: ryanslade
Add last_sync_at
, next_sync_at
and namespace_user_id
columns to the external_services table.
This change only adds the columns and updates the SQL level functions that update and scan columns so that we can unblock works on RFC 211.
One additional change is that we now populate the DeletedAt
field on types.ExternalService
which seems to have been missed before.
Part of: https://github.com/sourcegraph/sourcegraph/issues/12701