DbDsoStore and DbScanStore ingest data for the same party, therefore their UpdateHistory should contain exactly the same data. Except only the UpdateHistory of the DbScanStore is backfilled.

Duplicating the data and the backfilling process is a waste of storage and network resources.

• Document that the sv app will never be able to answer historical queries, and such queries will have to go through the scan API
• Stop ingesting UpdateHistory data in DbDsoStore
• Truncate the existing data in the database