Document how to create Widgy Owners in migrations

[rockymeza]

We need to document how to create Widgy Owners in a migration.

Here's what I just did:

from django.contrib.contenttypes.models import ContentType

from ..models import MyRootBucket

class Migration(DataMigration):
    def forwards(self, orm):
        "Write your forwards methods here."
        ct = ContentType.objects.get_for_model(MyRootBucket)
        orm['widgets.MyOwner'].objects.create(content=ct)

    def backwards(self, orm):
        "Write your backwards methods here."
        orm['widgets.MyOwner'].objects.all().delete()

But I don't know if it's correct.