Update Index Settings

[MichaelXavier]

I've hit a case where it would be useful to have this API so this is an issue do discuss the possible implementation. The documentation is refreshingly detailed about updating index settings:

https://www.elastic.co/guide/en/elasticsearch/reference/current/indices-update-settings.html

My first thoughts on a plan:

1. We can't use IndexSettings. The docs show a much more rich set of options that can be tweaked than IndexSettings provide.
2. You will get an error from the server if you provide an empty set of updates. Somewhere in the update type it should have a NonEmpty IndexSettingsUpdate.
3. IndexSettingUpdate would be a sum type over all the settings shown.
4. The type would then be something like updateIndexSettings :: MonadBH m => NonEmpty IndexSettingUpdate -> IndexName -> m Reply

Let me know what you think of the plan.

[bitemyapp]

@MichaelXavier zero things to object to in the proposal you've laid out here. Go for it!

One thing that caught me eye when I was reading the docs, the flipping around of index settings (refresh rate) for bulk indexing. Wondering how well that works and how dangerous it is. I need some AWS budget to play with :P