Add set security user ingest processor

[ng-druid]

Is your feature request related to a problem? Please describe

I would like to include the authenticated user id as part of a document using an ingest pipeline processor. Additionally, roles even claims in the token used to authenticate.

Describe the solution you'd like

Elasticsearch provides a set security processor already.

https://www.elastic.co/guide/en/elasticsearch/reference/current/ingest-node-set-security-user-processor.html

I think this would satisfy user id but uncertain on roles, claims.

Ideally, have an option to embed specific user info, entire object with exclusions as either a standard nested object or flat object.

Describe alternatives you've considered

none

Additional context

It could be that the set security processor exists just needs to be added to the docs.

[stephen-crawford]

[Triage] Hi @ng-druid, thanks for filing this issue. This seems like a good feature request. Going to mark as triaged.

[cwperks]

This may also be possible through the MapperPlugin extension point similar to mapper-size plugin.