feat: Added support for sts:ExternalId in modules/iam-assumable-role

[LAKostis]

Description

• Add support of sts:ExternalId

Motivation and Context

https://docs.aws.amazon.com/IAM/latest/UserGuide/id_roles_create_for-user_externalid.html - sometimes service integration require ExternalId instead of MFA.

Breaking Changes

None

How Has This Been Tested?

I've tested in my environment having this kind of setup:

module "iam_assume_role_in_prod_testrole" {
  source = "git::https://github.com/LAKostis/terraform-aws-iam.git//modules/iam-assumable-role?ref=feature/add-sts-externalid-support"

  trusted_role_arns = [
    "arn:aws:iam::${var.some_account_id}:root",
  ]

  create_role = true

  role_name         = "DatadogAWSIntegrationRole"
  role_requires_mfa = false

  sts_externalid = var.datadog_sts_id

  custom_role_policy_arns = [
    "arn:aws:iam::${data.aws_caller_identity.test.account_id}:policy/DatadogAWSIntegrationPolicy",
  ]

  providers = {
    aws = aws.test
  }
}

[antonbabenko]

Thanks for this addition, @LAKostis !

v2.15.0 has been just released.

[github-actions]

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