Elasticsearch output - Add support up to ES 7.x

[lpic10]

This PR adapts the index template to work on versions 6.x and 7.x while still supporting 5.x

Also it removes the mapping type on ES 7.x as mapping types are deprecated. Telegraf still sets the mapping type to "metrics" to keep backwards compatibility on previous ES versions.

Tested manually on versions 5.6, 6.0, 6.8 and 7.2

closes #5780
closes #4268

Required for all PRs:

• Signed CLA.
• Associated README.md updated.
• Has appropriate unit tests.

[sureshsubramaniam]

Is there a possibility to add Elasticsearch output to send to Elasticsearch service in AWS where it may need to be signed before initiating the connection similar to running a AWS proxy

[lpic10]

Is there a possibility to add Elasticsearch output to send to Elasticsearch service in AWS where it may need to be signed before initiating the connection similar to running a AWS proxy

Elasticsearch output uses Elastic client (https://github.com/olivere/elastic) and it seems to be possible with few changes: https://github.com/olivere/elastic/wiki/Using-with-AWS-Elasticsearch-Service

As I don't use AWS Elasticsearch myself it would be difficult for me to implement that correctly.
Anyway, I think you should open a new Feature Request.

[sureshsubramaniam]

Is there a possibility to add Elasticsearch output to send to Elasticsearch service in AWS where it may need to be signed before initiating the connection similar to running a AWS proxy

Elasticsearch output uses Elastic client (https://github.com/olivere/elastic) and it seems to be possible with few changes: https://github.com/olivere/elastic/wiki/Using-with-AWS-Elasticsearch-Service

As I don't use AWS Elasticsearch myself it would be difficult for me to implement that correctly.
Anyway, I think you should open a new Feature Request.

Thanks will look into the referenced Elastic client and create a raise a Feature request