Compute 7-Day Rolling Revenue

Lynx Analytics needs a time-based revenue feature for user behavior analysis. Write a PostgreSQL query that aggregates event revenue by user and calendar day, then calculates each user's trailing 7-day revenue for every day on which that user has an event.

The window must include the current calendar day and the six preceding calendar days. Treat a NULL revenue value as zero, and retain events whose user_id is NULL as a separate partition.

Requirements

1. Aggregate multiple events for the same user and calendar day before applying the rolling calculation.
2. Return user_id, event_day, daily_revenue, and rolling_7_day_revenue.
3. Use a time-based window frame rather than a fixed number of rows, because users may have gaps between active days.
4. Order the final results by user_id ascending with NULL users first, then by event_day ascending.