Migration for UFZ aggregation type values

It seems that the original migration to add a default aggregation type based on the current property_uri (https://codebase.helmholtz.cloud/hub-terra/sms/backend/-/blob/master/app/migrations/versions/0410c9cbc6cf_.py) did not work at UFZ.

So we have to add another migration there for the cases where the aggregation type is still null.