[BUG] policy_document_library ignores source_policy_documents

[dkoder20]

Describe the bug
aws_iam_source_policy_document does not follow the nested aws_iam_source_policy_document for scan because it ignores the source_policy_documents attribute in HCL as well as plan.

How you're running Regula
Please include versions of all relevant tools. Some examples:

• Regula v2.9.3
• OPA v0.43.1

Operating System
OS X

Steps to reproduce
Policy that addresses regula rule such as FG_R00100 in data.aws_iam_source_policy_document resource that is referenced in another data.aws_iam_source_policy_document inside the source_policy_documents attribute is not being scanned. Because of this the scan produces a false positive as the policy definition that addresses rule FG_R00100 is not scanned.

IaC Configuration

data "aws_iam_policy_document" "encryption_in_transit" {
  statement {
    sid     = "TLSEnforcement"
    actions = ["s3:*"]
    effect  = "Deny"
    resources = [
      "arn:aws:s3:::${aws_s3_bucket.this.id}/*",
      "arn:aws:s3:::${aws_s3_bucket.this.id}"
    ]
    condition {
      test     = "Bool"
      values   = [false]
      variable = "aws:SecureTransport"
    }
    condition {
      test     = "NumericLessThan"
      values   = [1.2]
      variable = "s3:TlsVersion"
    }
    principals {
      type        = "*"
      identifiers = ["*"]
    }
  }
}

data "aws_iam_policy_document" "combine_policy" {
  source_policy_documents = [
    data.aws_iam_policy_document.encryption_in_transit.json // source_policy_documents is ignored so this is never scanned
  ]

  ...
}

resource "aws_s3_bucket_policy" "default" {
  bucket = aws_s3_bucket.this.id
  policy = data.aws_iam_policy_document.combine_policy.json
}

resource "aws_s3_bucket" "this" {
  bucket        = "test-bucket"
}

Additional context
Add any other context about the problem here.