title: Migrate legacy database to cqrs/event sourcing view
body: <p>We got old legacy application with complex business logic which we need to rewrite. We consider to use cqrs and event sourcing. But it's not clear how to migrate data from the old database. Probable we need migrate it to the read database only, as we can't reproduce all the events to populate event store. But we atleast need to create some initial records in event store for each aggregate, like <code>AggregateCreated</code>? Or we need write a scripts and to use all the commands one by one to recreate aggregates in same way we will normally with event sourcing?</p>