Support for aggregation_dimensions?

[jpheneger]

I'm using this library to capture metrics for several node applications - I'd like to specify multiple dimensions in order to be able to filter within CloudWatch but once the dimensions are applied to a metric AWS does not provide aggregation across dimensions.

If I want to have a dimension for environment, instance_id, and release - I cannot get metrics that are aggregated for all metrics in the "prod" environment.

AWS addresses this with the aggregation_dimensions configuration (https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/CloudWatch-Agent-Configuration-File-Details.html#CloudWatch-Agent-Configuration-File-Metricssection).

Adding this to the library would be very helpful.