Populate person or group properties from a data warehouse table or materialized view, so warehouse columns become properties usable in feature flags, cohorts, and insights. Use when the user wants to "sync my Postgres columns to person properties", "map a warehouse table to people", "replace our daily identify cron", "update person properties from the warehouse", or asks for reverse ETL into PostHog. Covers picking the table and the identifier column, proposing a whole-table column mapping in one call, excluding identity and reserved properties, checking collisions with properties that already exist, and running the first backfill.
