ElasticSearch storage: Use multiple indices to make it possible to use curator for retention management

[leo-labs]

It should be possible to use instead of one very large index multiple indices e.g. one per week. That would allow the use of curator (https://www.elastic.co/guide/en/elasticsearch/client/curator/5.8/index.html) for automatic deletion of older data.

[leo-labs]

Right now, to delete old (older than 3 months) emails:

POST elasticsearch:9200/<index-name>/_delete_by_query
{
  "query": {
    "bool": {
      "filter" : [
                { "range" : { "firstProcessed" : { "lte" : "now-3M"}}}
       ]
    }
  }
}

To free up space:

http://elasticsearch:9200/<index-name>/_forcemerge?only_expunge_deletes=true
``