Ensure that host volumes are only on the required nodes

1-nixos-node/configuration.nix

@@ -47,14 +47,12 @@
         client = {
           enabled = true;
           host_volume = {
-            traefik = {
-              path = "/opt/traefik";
-              read_only = false;
-            };
-            postgres = {
-              path = "/opt/postgres";
+%{ for volume in host_volumes ~}
+            ${volume} = {
+              path = "/opt/${volume}";
               read_only = false;
             };
+%{ endfor ~}
           };
           cni_path = "$${pkgs.cni-plugins}/bin";
         };
@@ -93,10 +91,10 @@
   systemd.tmpfiles.rules = [
     # Fix issue where nomad needs alloc_mounts to be writable
     "d /var/lib/alloc_mounts 0755 root root -"
-    # Create a directory for Traefik to store its data (tls certs, etc.)
-    "d /opt/traefik 0755 root root -"
-    # Create a directory for Postgres to store its data
-    "d /opt/postgres 0755 root root -"
+%{ for volume in host_volumes ~}
+    # Create a directory for ${volume} to store its data
+    "d /opt/${volume} 0755 root root -"
+%{ endfor ~}
   ];
 
   # Open ports in the firewall. 80/443 are for HTTP/HTTPS (terraform), 464X are the default ports for Nomad, 830X are the default ports for Consul.