Add variable to manage the CreateLogGroup permission

[jake-naughton]

Is your request related to a new offering from AWS?

• Already exists.

Is your request related to a problem? Please describe.

I have to manage IAM roles outside of this module because it enforces logs:CreateLogGroup permission when the module provisions the CloudWatch log group. However, there are many cases where you don't need or want this permission attached to your lambda and it is a nuisance when you are dealing with ephemeral environments. The problem is described in this issue:
#342

Describe the solution you'd like.

To add a variable that allows for the logs:CreateLogGroup to be turned off even when the module is responsible for provisioning the CloudWatch logs. By default it would be on so no change in behaviour.

variable "attach_create_log_group_permission" {
  description = "..."
  type             = bool
  default        = true
}

data "aws_iam_policy_document" "logs" {
  count = local.create_role && var.attach_cloudwatch_logs_policy ? 1 : 0

  statement {
    effect = "Allow"

    actions = compact([
      !var.use_existing_cloudwatch_log_group && var.attach_create_log_group_permission ? "logs:CreateLogGroup" : "",
      "logs:CreateLogStream",
      "logs:PutLogEvents"
    ])

    resources = flatten([for _, v in ["%v:*", "%v:*:*"] : format(v, local.log_group_arn)])
  }
}

Describe alternatives you've considered.

Creating my own IAM role outside of the module and passing it in. Could also create the CloudWatch log group outside of the module.

Additional context

Happy to put up a PR for this improvement if it is acceptable.

[github-actions]

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[jake-naughton]

Any thoughts on this?

[antonbabenko]

Hi @jake-naughton !

Please make a PR with the proposed change.

[jake-naughton]

Hi @antonbabenko, I have raised the PR here: #514

[github-actions]

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