If set to true then wait for the changes made by the request to be made
visible by a refresh before replying. This does not force an immediate
refresh, rather, it waits for a refresh to happen. Elasticsearch
automatically refreshes shards that have changed every
index.refresh_interval which defaults to one second. That setting is
dynamic. Calling the Refresh API or setting refresh to true on any of the
APIs that support it will also cause a refresh, in turn causing already
running requests with refresh=wait_for to return.