Use hut-substituter module in owl{1,2} and raccoon

m/module/hut-substituter.nix

@@ -0,0 +1,10 @@
+{ config, ... }:
+{
+  nix.settings =
+    # Don't add hut as a cache to itself
+    assert config.networking.hostName != "hut";
+    {
+      substituters = [ "https://jungle.bsc.es/cache" ];
+      trusted-public-keys = [ "jungle.bsc.es:pEc7MlAT0HEwLQYPtpkPLwRsGf80ZI26aj29zMw/HH0=" ];
+    };
+}

m/owl1/configuration.nix

@@ -8,6 +8,7 @@
     ../module/slurm-client.nix
     ../module/slurm-firewall.nix
     ../module/debuginfod.nix
+    ../module/hut-substituter.nix
   ];
 
   # Select the this using the ID to avoid mismatches

m/owl2/configuration.nix

@@ -8,6 +8,7 @@
     ../module/slurm-client.nix
     ../module/slurm-firewall.nix
     ../module/debuginfod.nix
+    ../module/hut-substituter.nix
   ];
 
   # Select the this using the ID to avoid mismatches

m/raccoon/configuration.nix

@@ -3,6 +3,7 @@
 {
   imports = [
     ../common/base.nix
+    ../module/hut-substituter.nix
   ];
 
   # Don't install Grub on the disk yet