Switched to binds, volume management, new API

volumes.nix

@@ -0,0 +1,15 @@
+{ pkgs, config, ... }:
+let
+  cfg = config.services.userdata;
+in
+{
+  fileSystems = { } // builtins.listToAttrs (builtins.map
+    (volume: {
+      name = "${volume.mountPoint}";
+      value = {
+        device = "${volume.device}";
+        fsType = "${volume.fsType}";
+      };
+    })
+    cfg.volumes);
+}