dns_keys output added to the dns module (#97)

* dns_keys output added to the dns module, so DNSSEC attributes like DS entry will be outputed if DNSSEC configuration is provided

* Fix confition for dns_keys data source

modules/dns/outputs.tf

@@ -38,3 +38,8 @@ output "name_servers" {
   description = "The DNS zone name servers."
   value       = try(local.zone.name_servers, null)
 }
+
+output "dns_keys" {
+  description = "DNSKEY and DS records of DNSSEC-signed managed zones."
+  value       = local.dns_keys
+}