add sigv4 signing to client for aws es support

[chrislujan]

Added support for AWS auth

When the following attributes are present, a different client will be created.

  aws_access_key_id
  aws_secret_access_key
  region

[kares]

Hey, thanks for the PR. this seems to be concerning Amazon's ES offering, right?
if that is the case I believe Amazon decided to fork Elastic's ES plugins to support their specific extensions ...

[chrislujan]

I haven't seen one for this though. I have only seen this https://github.com/awslabs/logstash-output-amazon_es which is close but not a filter plugin.

[chrislujan]

still nothing from amazon, any chance of getting this merged?

[seanmcelroy]

This has broad applicability as an enhancement so AWS ES can be queried through a filter plugin, even in an otherwise pure Elastic.co Elastic environment. I'd love to see this support offered in this plugin.

[dan-ih]

Bump