Aggregate events

Exact counts for ONE event name, in one call — optionally broken down by the values of one payload property. Use this instead of listing events and counting them yourself: a page of results is capped and tells you nothing about how many exist beyond it, so counting a page produces a number that looks right and is wrong. total counts events; unique_people counts distinct people, and the two routinely differ because one person can fire the same event many times — never report one as the other. Events missing the group_by property group under value: null, and events whose subject is a custom object rather than a person count toward total but not unique_people. Within a breakdown the bucket counts sum to total, but the bucket unique_people do NOT sum to the top-level unique_people — one person who fired the event under two different values is counted in both buckets, so never add them up. The buckets are capped: when groups_truncated is true the buckets shown do NOT add up to total and there are more values than listed — say so rather than presenting the breakdown as the whole picture. This aggregates ONE event name; it cannot relate two different events, so it cannot compute a conversion rate between them on its own.