Generate an ID for an eventedit

The add_id processor generates a unique ID for an event.

 - add_id: ~

The following settings are supported:

(Optional) Field where the generated ID will be stored. Default is @metadata._id.
(Optional) Type of ID to generate. Currently only elasticsearch is supported and is the default. The elasticsearch type generates IDs using the same algorithm that Elasticsearch uses for auto-generating document IDs.