Using dynamic blocks within kafka_acl

[RichCranney]

I've recently started using the mongey/kafka provider to automate my Amazon MSK topic creation and I'm looking to streamline access control by use of a module.

In the module it will loop through a number of users, that are passed in JSON format and apply either READ or WRITE permissions to the list of users. From the error message I'm getting, it looks like the dynamic block is not supported, is there any way to have this support in upcoming versions?

My code is as follows:

resource "kafka_acl" "msk_topic_module_acl" {
  count = length(var.permissions)

  resource_name       = "${var.topic_name}"
  resource_type       = "Topic"
  acl_operation       = var.permissions[count.index].access
  acl_permission_type = "Allow"

  dynamic "principal" {
    for_each = toset(var.permissions[count.index].usernames)
    content {
      acl_principal       = "User:${principal.value}"
      acl_host            = "*"
    }
  }

  depends_on          = [kafka_topic.msk_topic_module_topic]
}

And user access is passed to the permissions variable in the following format:

    permissions = [
        {
            "usernames": [
              "Bob",
              "Jon",
              "Bill"
            ],
            "access":   "Read"
        }
    ]

The error I get in terraform is as follows:
Blocks of type "principal" are not expected here.