Bump minimum Terraform to 0.12.9

[dpiddockcmp]

PR o'clock

Description

Additions in #602 trigger a bug in older terraforms. It was fixed in 0.12.9.

Error: Invalid for_each set argument

  on ../../node_groups.tf line 30, in resource "aws_iam_role_policy_attachment" "node_groups_additional_policies":
  30:   for_each = toset(var.workers_additional_policies)

The given "for_each" argument value is unsuitable: "for_each" supports maps
and sets of strings, but you have provided a set containing type dynamic.

Checklist

• Change added to CHANGELOG.md. All changes must be added and breaking changes and highlighted
• CI tests are passing
• README.md has been updated after any changes to variables and outputs. See https://github.com/terraform-aws-modules/terraform-aws-eks/#doc-generation

[max-rocket-internet]

Cool. Thanks as always @dpiddockcmp

[github-actions]

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