Active subscription base per period.

• Returns an array of {period, group_by, group_by_public_id, group_by_name, count} rows, one per period (and per group_by value when set).
• count: the number of subscriptions active at the close of the period. The last row is the number active at the end of date_range (end date included), so a range ending mid-period reads the base on that date.
• Auto-renewing, cancelled-but-not-expired and grace-period subscriptions all count as active. Family-shared subscriptions and transfers are excluded.
• Unit: count of active subscriptions. A stock, not a flow: never sum it across periods. Read the last period for the current base.
• The paid_subscription_movements flows do not reconcile exactly with this base: a close is not the previous close plus net_movement_count, because the two follow different rules. This base counts every ACTIVATE and DEACTIVATE, keeps a grace-period subscription active until its DEACTIVATE, and ends a paid segment when the offer changes from paid to free.
• For the exact base on a date, read the last row of a date_range that ends on that date, or use periodicity=DAY, not a close plus movements.
• Recommended periodicity: MONTH (WEEK for a close look at the last few months).
• Single application only.

Required scope: analytics.dashboards:view