v2.0.0

Changed

• Breaking. Requires rasuvaeff/yii3-ab-testing ^2.0.
• Breaking. Trackers and the message factory take core events
  (ExposureEvent, ConversionEvent) instead of an Assignment and a goal.
  The tracker's optional $eventId argument is gone: the core already minted
  the identity, and the tracker now always passes $event->eventId to
  Outbox::record(), so the message id and the payload's event_id cannot
  disagree.
• Breaking. Payload v2 is the canonical schema v2 row, produced by core's
  CanonicalEventSerializer rather than assembled here. Building it locally is
  how the two delivery paths drifted in v1 — each dropped different fields and
  nothing noticed.
• Breaking. AbTestingClickHouseRoutes::map() takes no arguments and
  targets the tables and column order owned by
  yii3-ab-testing-clickhouse's AnalyticsSchemaV2. legacyV1Map() returns
  the old routes for draining messages queued before the upgrade.

Removed

• Breaking. AllowListAnalyticsContextPolicy, AnalyticsContextPolicyInterface
  and SystemClock moved to the core. The allow-list is applied once, when the
  facade builds the event, so every delivery path filters identically; keeping
  it here applied it to the durable path only.
• The context params key, for the same reason.

See UPGRADE.md for the migration steps.