Upgrade RDS (to PostgreSQL 13 + certificate authority) (#112)

Fixes #110

Author: magul

db.tf

@@ -16,7 +16,7 @@ resource "aws_db_instance" "db" {
   identifier = "main-postgres"
 
   engine         = "postgres"
-  engine_version = "12.19"
+  engine_version = "13.18"
 
   instance_class    = "db.t3.micro"
   allocated_storage = 8
@@ -31,6 +31,8 @@ resource "aws_db_instance" "db" {
 
   final_snapshot_identifier = "main-postgres-final-snapshot"
 
+  ca_cert_identifier = "rds-ca-rsa2048-g1"
+
   depends_on = [
     random_password.db_password,
     aws_db_subnet_group.private,