Refactor: optionally randomize resource names

[sanderginn]

• Part of https://github.com/sourcegraph/sourcegraph/issues/44239

Adds a randomize_resource_names variable that allows random resource names to be generated.
This is less critical than its GCP counterpart due to the fact that AWS already generates random IDs, but for organizing resources it is still valuable to set resource names.

Due to a bug in the AWS provider running terraform apply twice would be needed to set the calculated tags. To circumvent this, the default_tags block in the provider config sets null for these tags:

default_tags {
  tags = {
    "Name"         = null
    "executor_tag" = null
    "deployment"   = "sourcegraph-executors"
  }
}

Test plan

Tested on scaletesting instance.

The following plan is produced when planning these changes on an existing deployment using v4.5.0 of the module with randomize_resource_names = false. There are some tags that are added because they have defaults added now, but those don't have functional impacts. The name tag for aws_autoscaling_group.autoscaler is updated from sourcegraph_executor to sourcegraph_executors to align with other naming conventions.

Terraform will perform the following actions:

  # module.executors.module.aws-docker-mirror.aws_security_group.default[0] will be updated in-place
  ~ resource "aws_security_group" "default" {
        id                     = "sg-0c3a16702f8ae3721"
        name                   = "SourcegraphExecutorsDockerMirrorAccess"
      ~ tags                   = {
          + "Name" = "SourcegraphExecutorsDockerMirrorAccess"
        }
      ~ tags_all               = {
          + "Name"       = "SourcegraphExecutorsDockerMirrorAccess"
            # (1 unchanged element hidden)
        }
        # (7 unchanged attributes hidden)
    }

  # module.executors.module.aws-executor.aws_autoscaling_group.autoscaler will be updated in-place
  ~ resource "aws_autoscaling_group" "autoscaler" {
        id                        = "sourcegraph_executors"
        name                      = "sourcegraph_executors"
        # (23 unchanged attributes hidden)


      - tag {
          - key                 = "name" -> null
          - propagate_at_launch = true -> null
          - value               = "sourcegraph_executor" -> null
        }
      + tag {
          + key                 = "name"
          + propagate_at_launch = true
          + value               = "sourcegraph_executors"
        }
        # (2 unchanged blocks hidden)
    }

  # module.executors.module.aws-executor.aws_iam_instance_profile.instance will be updated in-place
  ~ resource "aws_iam_instance_profile" "instance" {
        id          = "sourcegraph__executors"
        name        = "sourcegraph__executors"
      ~ tags        = {
          + "Name" = "sourcegraph__executors"
        }
      ~ tags_all    = {
          + "Name"       = "sourcegraph__executors"
            # (1 unchanged element hidden)
        }
        # (5 unchanged attributes hidden)
    }

  # module.executors.module.aws-executor.aws_launch_template.executor will be updated in-place
  ~ resource "aws_launch_template" "executor" {
      ~ default_version                      = 1 -> (known after apply)
        id                                   = "lt-0b1c2bb507662dc30"
      ~ latest_version                       = 1 -> (known after apply)
        name                                 = "sourcegraph_executor-template-20230304103845369900000002"
        tags                                 = {}
        # (17 unchanged attributes hidden)





      + tag_specifications {
          + resource_type = "instance"
        }
        # (4 unchanged blocks hidden)
    }

  # module.executors.module.aws-executor.aws_security_group.metrics_access[0] will be updated in-place
  ~ resource "aws_security_group" "metrics_access" {
        id                     = "sg-03830ca9ad561e223"
        name                   = "SourcegraphExecutorsMetricsAccess"
      ~ tags                   = {
          + "Name" = "SourcegraphExecutorsMetricsAccess"
        }
      ~ tags_all               = {
          + "Name"       = "SourcegraphExecutorsMetricsAccess"
            # (1 unchanged element hidden)
        }
        # (7 unchanged attributes hidden)
    }

Plan: 0 to add, 5 to change, 0 to destroy.

[eseliger]

Should we enable this by default in the examples, to highlight best practices?