How to create Postgresql RDS reader node with terraform

Terraform Providers AWS
1

we have existing PostgreSQL AWS RDS instance with writer node, and it was created through terraform but now I want to create reader node to the existing RDS db instance Please help me with terraform code to add reader node to below code.

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# RDS Aurora
#############
module "pms_prod_aurorapostgresql" {
  source = "../TFModules/RDS/RDSAurora/"
  providers = {
    aws = aws.production
  }
  name                            = "pms-prod-postgresql"
  engine                          = "aurora-postgresql"
  engine_version                  = "13.3"
  database_name                   = "pms"
  DBSubnetGroupName               = module.EKSprodVPC.DBSubnetGroupName
  vpc_id                          = module.EKSprodVPC.VPCID
  replica_count                   = 1
  replica_scale_enabled           = true
  replica_scale_min               = 1
  replica_scale_max               = 4
  monitoring_interval             = 60
  instance_type                   = "db.r6g.2xlarge"
  apply_immediately               = true
  skip_final_snapshot             = true
  db_parameter_group_name         = aws_db_parameter_group.pms_prod_aurora_postgres_db_parameter_group.id
  db_cluster_parameter_group_name = aws_rds_cluster_parameter_group.pms_prod_aurora_postgres_cluster_parameter_group.id
  //  enabled_cloudwatch_logs_exports = ["audit", "error", "general", "slowquery"]
  allowed_cidr_blocks = ["172.18.0.0/11", "192.168.0.0/16", "10.0.1.0/9"]
  tags = merge(var.CoreTags, {
    "Creator" = "tony"
    "Owner"   = "infra"
  })
}

resource "aws_db_parameter_group" "pms_prod_aurora_postgres_db_parameter_group" {
  name        = "pms-prod-aurora-db-postgres13-parameter-group"
  family      = "aurora-postgresql13"
  description = "pms-prod-aurora-db-postgres13-parameter-group"
  tags = merge(var.CoreTags, {
    "Creator" = "tony"
    "Owner"   = "infra"
  })
  provider    = aws.production
}

resource "aws_rds_cluster_parameter_group" "pms_prod_aurora_postgres_cluster_parameter_group" {
  name        = "pms-prod-aurora-postgres13-cluster-parameter-group"
  family      = "aurora-postgresql13"
  description = "pms-prod-aurora-postgres13-cluster-parameter-group"
  tags = merge(var.CoreTags, {
    "Creator" = "tony"
    "Owner"   = "infra"
  })  
  provider    = aws.production
}

Regards,
Shilpa