Lists and segments: people in them, who joined and left in a period

Each list (people now) and segment (people as of its last check; unpublished ones have none) with the people who joined and left in the period, from *List Joined*, *List Left*, *Segment Entered* and *Segment Exited*. A segment counts joins from when it was published: publishing builds it without events (D164). `locale` narrows to people in those locales.

curl -X GET 'https://api.postforge.dev/v1/analytics/audiences'

{  "items": [    {      "id": "string",      "kind": "list",      "name": "string",      "people": 0,      "checkedAt": "2019-08-24T14:15:22Z",      "joined": 0,      "left": 0    }  ],  "total": 0,  "page": 0,  "pageSize": 0}