[terraform-ibm-landing-zone] Retention Policy for COS Buckets.

[Xallarap]

Description

IBM Cloud for Financial Services requires a Retention Policy to be set for all buckets containing log data.

While IBM Terraform Module "ibm_cos_bucket" provides the parameters for this, the Landing Zone "cos.tf" file does not provide it.
See retention rule in:
https://registry.terraform.io/providers/IBM-Cloud/ibm/latest/docs/resources/cos_bucket

Affected modules

https://github.com/terraform-ibm-modules/terraform-ibm-landing-zone/blob/main/cos.tf

The logic in "cos.tf" needs to be enhanced to support the following example snippet from the ibm_cos_bucket

### Configure retention rule on COS bucket

resource "ibm_cos_bucket" "retention_cos" {
  bucket_name          = "a-bucket-retention"
  resource_instance_id = ibm_resource_instance.cos_instance.id
  region_location      = "jp-tok"
  storage_class        = standard
  hard_quota           = 1024
  force_delete        = true
  retention_rule {
    default = 1
    maximum = 1
    minimum = 1
    permanent = false
  }
}

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[kierramarie]

PR merged. Closing issue.