Support Elasticsearch API key authentication

[cfeltz34]

There's no Elasticsearch API key option in here: https://docs.fluentbit.io/manual/pipeline/outputs/elasticsearch

Is there a way to use an api key by setting the header or by setting the api key.

example:
Header Authorization ${ELASTICSEARCH_APIKEY}
or
api_key: ${ELASTICSEARCH_APIKEY}

See also : #8357

[patrick-stephens]

Presumably not Elastic Cloud? https://docs.fluentbit.io/manual/pipeline/outputs/elasticsearch#fluent-bit--elastic-cloud
Just checking - I don't use it but there is a way to pass Elastic Cloud creds if that's what you were after.