I am using terraform to create an SNS Queue. I am also creating my own SNS policy file

Terraform Code :-

variables.tf

variable "awsAccId" {
   default = "111222433"
}

variable "region" {
  default = "ca-central-1"
}

locals.tf

sns_topic_name = "fail-notification"
fail_noti_topic_arn = "arn:aws:sns:${var.region}:${var.awsAccId}:${local.sns_topic_name }"

resource "aws_sns_topic" "fail-noti-topic" {
  name = "${local.sns_topic_name }"
}

resource "aws_sns_topic_policy" "fail-noti-topic-policy" {
  arn = aws_sns_topic.fail-noti-topic.arn

  policy = file("policy/sns-policy.json")
}

resource "aws_sns_topic_subscription" "fail-noti-topic" {
 ...
 ...
 
}

Inside policy(folder) -> sns-policy.json (file)

{
  "Version": "2012-10-17",
  "Id": "${local.sns_topic_name }_policy_ID",
  "Statement": [
    {
      "Sid": "${local.sns_topic_name}_statement_ID",
      "Effect": "Allow",
      "Principal": {
        "AWS": "*"
      },
      "Action": [
        "SNS:Publish",
        "SNS:RemovePermission",
        "SNS:SetTopicAttributes",
        "SNS:DeleteTopic",
        "SNS:ListSubscriptionsByTopic",
        "SNS:GetTopicAttributes",
        "SNS:AddPermission",
        "SNS:Subscribe"
      ],
      "Resource": "${local.fail_noti_topic_arn}",
      "Condition": {
        "StringEquals": {
          "AWS:SourceOwner": "{var.awsAccId}"
        }
      }
    }
  ]
}

I was expecting that the variables in the json would resolve and I would get the exact values as described in the locals.tf and variables.tf file.

Instead, the access policy, as shown in the AWS console is

I tried using policy = jsonencode(file("policy/sns-policy.json")) , but I am getting another error , while terraform apply that (something like this)

policyerror Attribute is not valid.

This error is not there during the planning phase.

I also tried something like

resource "aws_sns_topic_policy" "fail-noti-topic-policy" {
  arn = aws_sns_topic.fail-noti-topic.arn

  policy = <<POLICY
{
  "Version": "2012-10-17",
  "Id": "${local.sns_topic_name }_policy_ID",
  "Statement": [
    {
      "Sid": "${local.sns_topic_name}_statement_ID",
      "Effect": "Allow",
      "Principal": {
        "AWS": "*"
      },
......

POLICY

But, this too does NOT resolve the variables with their corresponding values.

What should I do, to resolve the variables in the policy JSON files, so that I get their actual values, instead of the variables themselves ?