feat(nimbolus): init a http terraform backend

modules/nixos/nimbolus-tf.nix

@@ -10,7 +10,6 @@
 }:
 let
   inherit (lib)
-    concatMapAttrsStringSep
     escapeShellArg
     getExe
     mkEnableOption
@@ -24,6 +23,12 @@ let
     str
     ;
 
+  # from nixpkgs, commit b1371135b5db3fcf728114d92d5bd0218109598a
+  # FIXME: Should be replaced by nixpkgs lib when going to nixos-25.05
+  concatMapAttrsStringSep =
+    sep: f: attrs:
+    lib.concatStringsSep sep (lib.attrValues (lib.mapAttrs f attrs));
+
   cfg = config.services.nimbolus-tf;
 in
 {