[Enhancement]: skip_existing support for aws_cloudwatch_log_group

[G-Rath]

Description

This is something of a follow-on from #26752, making it a bit nicer to use by allowing aws_cloudwatch_log_group resources to skip creation if a matching group already exists, and do an update instead.

There has been discussion about supporting this in Terraform core, with I think hashicorp/terraform#26364 being the latest iteration of this, but it's slow going and unlikely to be resolved soon; there has also been #20635 which was for general resources but mentioned aws_cloudwatch_log_group - that was closed in favor of #14394 though that issue is about better error messaging at plan-time.

While this behaviour would mean the plan shown for resources with skip_existing enabled could arguably be slightly wrong because it would not reflect if the group existed and if so what changes would be made, I think that is acceptable given this is an opt-in flag, has similar value as skip_destroy especially when paired with things like the CloudWatch Agent that can automatically create log groups if they don't exist, and from what I can tell it sounds like improving this case would require a change in Terraform core which will probably take a while.

Affected Resource(s) and/or Data Source(s)

• aws_cloudwatch_log_group

Potential Terraform Configuration

resource "aws_cloudwatch_log_group" "yada" {
  name = "Yada"

  skip_destroy  = true
  skip_existing = true

  tags = {
    Environment = "production"
    Application = "serviceA"
  }
}

References

No response

Would you like to implement a fix?

Yes

[github-actions]

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[G-Rath]

I've got an implementation for this with acceptance tests - will open a PR shortly