v2.0.0

Added

• Versioned analytics event contract: ExposureEvent, ConversionEvent,
  DecisionReason, AssignmentSource and AssignmentReceipt.
• EventSerializer with CanonicalEventSerializer — one wire format shared by
  every delivery path, with the row shapes published as importable Psalm types.
• EventIdGenerator with three implementations: Uuid7EventIdGenerator
  (default, no dependencies), SymfonyUidEventIdGenerator and
  RamseyUuidEventIdGenerator.
• AttributionWindow and RepeatedConversionPolicy — the reporting rules that
  decide what conversion numbers mean.
• SystemClock, and clock / eventIds / contextPolicy arguments on
  AbTesting.
• AbTesting::trackConversionForReceipt() for a conversion in a later request.
• fixtures/golden-event-v2.json, shipped so adapters can assert the same rows.
• ConfigurationAwareAssignmentStore, moved here from yii3-ab-testing-web so
  the cookie store and the database store can share it without depending on
  each other.

Changed

• Breaking. ExposureTracker and ConversionTracker take an event instead
  of an Assignment and a goal.
• Breaking. Assignment replaces isForced, isFallback, isSticky and
  isTargetingMismatch properties with a reason / source pair and
  same-named methods.
• Breaking. AnalyticsContextPolicy (was
  AnalyticsContextPolicyInterface in yii3-ab-testing-outbox) moved into the
  core, so every delivery path applies one allow-list.
• Breaking. Logger sinks emit the canonical row under an event key,
  making them the log-shipping delivery path.
• Breaking. An empty conversion goal now reports
  Event field "goal" must not be empty.
• trackExposure() and trackConversion() return the recorded event.

See UPGRADE.md for the migration steps.