onPartitionAssigned
abstract suspend fun onPartitionAssigned(partition: Int, afterToken: ExternalSourceToken?, txIndexer: TxIndexer)
Called when partition is assigned to this node, to run the source's poll loop.
Resume from just after afterToken - the token of the last tx already indexed for this partition, or null to start from the beginning - submitting each upstream event via txIndexer.
Implementors must follow Kotlin's prompt cancellation guarantees - when the coroutine executing this method is cancelled, the implementor must clean up and cede control as soon as possible.