Use statement prefix IDs for lambda permissions

[zoonage]

We had an issue where the JSON blob for the CloudWatch events config was >8192 bytes causing CloudWatch to reject the change.

To get around this we used this module multiple times with the same team name with a smaller list of repositories.

We got a name collision on the Lambda permissions. To resolve this we would like to use prefixes.

[zoonage]

@itsdalmo

[zoonage]

Apologies, going to tag everyone in the telia-oss org as itsdalmo no longer appears to be in it.

@mahe54 @manitua @mhadaily @mhd999 @Natanande @rickardl is it possible to get a review on this please?

[larstobi]

@zoonage In order not to force changes on existing uses of this, a conditional enablement of the statement_id_prefix would be preferable.

May I suggest adding a bool input variable defaulting to false called something like use_sid_prefix and then using it to determine whether or not to use statement_id_prefix or statement_id.

i.e.
variables.tf

variable "use_sid_prefix" {
  type = bool
  default = false
}

main.tf

resource "aws_lambda_permission" "main" {
  statement_id  = var.use_sid_prefix ? null : "concourse-${var.name}-github-lambda-permission"
  statement_id_prefix = var.use_sid_prefix ? "concourse-${var.name}-github-lambda-permission-" : null
}

[zoonage]

Hi @larstobi seems sensible for backwards compatibility, I've updated the PR accordingly