Add new plugin metrics-reservation-utilization.rb

[boutetnico]

Pull Request Checklist

Is this in reference to an existing issue? No

General

• [x] Update Changelog following the conventions laid out here

• [ ] Update README with any necessary configuration snippets

• [ ] Binstubs are created if needed

• [ ] RuboCop passes

• [ ] Existing tests pass

New Plugins

• [ ] Tests

• [x] Add the plugin to the README

• [ ] Does it have a complete header as outlined here

Purpose

New plugin allowing to retrieve metrics about Reserved Instances utilization.

Example usage:

$ ruby /etc/sensu/plugins/metrics-reservation-utilization.rb
sensu.aws.reservation_utilization.utilizations_by_time.utilization_percentage 100 1563667200
sensu.aws.reservation_utilization.utilizations_by_time.purchased_hours 1584 1563667200
sensu.aws.reservation_utilization.utilizations_by_time.total_actual_hours 1584 1563667200
sensu.aws.reservation_utilization.utilizations_by_time.unused_hours 0 1563667200
sensu.aws.reservation_utilization.utilizations_by_time.on_demand_cost_of_ri_hours_used 30.288 1563667200
sensu.aws.reservation_utilization.utilizations_by_time.net_ri_savings 9.936 1563667200
sensu.aws.reservation_utilization.utilizations_by_time.total_potential_ri_savings 9.936 1563667200
sensu.aws.reservation_utilization.utilizations_by_time.amortized_upfront_fee 0 1563667200
sensu.aws.reservation_utilization.utilizations_by_time.amortized_recurring_fee 20.352 1563667200
sensu.aws.reservation_utilization.utilizations_by_time.total_amortized_fee 20.352 1563667200

Known Compatibility Issues

None