ec_deployment: Add autoscaling support

[marclop]

Description

Adds support for autoscaling.

The PR has been split in multiple commits to make reviewing easier.

data "ec_stack" "latest" {
  version_regex = "latest"
  region        = "us-east-1"
}

resource "ec_deployment" "example_minimal" {
  region                 = "us-east-1"
  version                = data.ec_stack.latest.version
  deployment_template_id = "aws-io-optimized-v2"

  elasticsearch {
    autoscale = "true"

    topology {
      id   = "cold"
      size = "8g"
    }

    topology {
      id   = "hot_content"
      size = "8g"

      autoscaling {
        // Optionally change the policy max size.
        // max_size = "29g"
      }
    }

    topology {
      id   = "ml"
      size = "1g"

      autoscaling {
        // Optionally change the policy max size.
        // max_size = "29g"
        // Optionally change the policy min size.
        // min_size = "1g"
      }
    }

    topology {
      id   = "warm"
      size = "16g"
    }
  }

  kibana {}

  apm {}

  enterprise_search {}
}

Related Issues

Closes #258

How Has This Been Tested?

Manual, unit and acceptance tests.

Types of Changes

• New feature (non-breaking change which adds functionality)

[Kushmaro]

ah another question - @marclop , given "autoscaling = true"
will the autoscaling object be mandatory (from a users's perspective)?

[marclop]

@Kushmaro it's optional at the moment. Since the policy settings can come from the Deployment Template it doesn't make much sense to make it mandatory.

[Kushmaro]

Agree @marclop :)
I was just making sure that having autoscaling = "true" won't cause a weird user behaviour.

LGTM

[karencfv]

Looks great! 👌

Thanks for adding datasource support as well!