nixos/powerdns, nixos/pdns-recurser: Symlink configuration into /etc

This places a symlink to the running configuration where the admin
tools expect it, allowing users to control the powerdns server or
recursor without manually specifying a config file.

nixos/modules/services/networking/pdns-recursor.nix

@@ -159,6 +159,8 @@ in {
 
   config = mkIf cfg.enable {
 
+    environment.etc."powerdns-recursor".source = configDir;
+
     services.pdns-recursor.settings = mkDefaultAttrs {
       local-address = cfg.dns.address;
       local-port    = cfg.dns.port;

nixos/modules/services/networking/powerdns.nix

@@ -38,6 +38,8 @@ in {
 
   config = mkIf cfg.enable {
 
+    environment.etc.powerdns.source = finalConfigDir;
+
     systemd.packages = [ pkgs.pdns ];
 
     systemd.services.pdns = {