Arion: Add volman

hosts/franz/arion/volman/arion-compose.nix

@@ -0,0 +1,16 @@
+{pkgs, ...}: {
+  project.name = "volman";
+
+  docker-compose.volumes = {};
+
+  services = {
+    volman.service = {
+      image = "ubuntu";
+      container_name = "volman";
+      useHostStore = true;
+      command = "sleep infinity";
+      volumes = [
+      ];
+    };
+  };
+}

hosts/franz/arion/volman/arion-pkgs.nix

@@ -0,0 +1,6 @@
+# Instead of pinning Nixpkgs, we can opt to use the one in NIX_PATH
+import <nixpkgs> {
+  # We specify the architecture explicitly. Use a Linux remote builder when
+  # calling arion from other platforms.
+  system = "x86_64-linux";
+}