Function strategy_from_catalog_json 

pub(crate) fn strategy_from_catalog_json(
    json: &str,
) -> Result<Option<AutoScalingStrategy>, String>

Parse the strategy jsonb column of mz_internal.mz_cluster_auto_scaling_strategies (fetched as text). The column is JSON null for a cluster whose policy was just removed while a burst still lingers, which maps to None like a missing row.