Add ability to re-index on demand

should we support some kind of polling mechanism for rarely-updated plugins or that don't have notifications? Our current answer is use a recurring timed job to reindex (and preferably use a separate resource group). Maybe that's enough? Perhaps just something needs spelling out in deployment notes. Examples: Murano team is interested in searchlight indexing, but doesn't have notifications and not sure when they'll be able to add. They don't think it needs to be real time.
Indexing right now is separate process (searchlight-manage)
Can add an option --interval X where x is every X seconds that is should repeat.
Li +1
Brian -1 (followed by maybe-ness but not convinced)
Lei: +1
David: +1
Travis: +1
Nanhai: +1