Minor Description
The AsyncIndexUpdate background thread handles the async update of any index (usually lucene for now, but it could be any index, really).
Besides the debug run logs, there is not much info on what the status is, if it's still running or not, etc.
I'm going to add some basic status updates, like async-status which can be running or done, async-start which indicates the start time of the async index thread (null if it's not running) and async-done which will indicate the last finish time (null if it's still running).
These bits of info should be enough to be able to tie in some code to fetch the index status grammatically.
Lastly, the status properties will be on the oak:index node, even if the async indexer relies on a hidden node :async which (I think) exists under the root node directly.