Function mz_catalog::durable::persist::fetch_catalog_upgrade_shard_version

async fn fetch_catalog_upgrade_shard_version(
    persist_client: &PersistClient,
    upgrade_shard_id: ShardId,
) -> Option<Version>

Fetch the persist version of the catalog upgrade shard, if one exists. A version will not exist if we are creating a brand-new environment.