* The callback must fully duck-type test the object, since can be any model class.
* @param array $params Additional options:
* - channel: the name of the update event stream.
- * Default: WANObjectCache::DEFAULT_PURGE_CHANNEL.
* - initialStartWindow: seconds back in time to start if the position is lost.
* Default: 1 hour.
* - logger: an SPL monolog instance [optional]