make nixos.nix reusable rather than opinionated

Signed-off-by: Kiara Grouwstra <kiara@procolix.eu>

deployment/check/data-model-ssh/nixosTest.nix

@@ -4,9 +4,10 @@
   ...
 }:
 let
+  inherit (import ./constants.nix) pathToRoot pathFromRoot;
   inherit (pkgs) system;
   deployment-config = {
-    inherit (import ./constants.nix) pathToRoot;
+    inherit pathToRoot pathFromRoot;
     nodeName = "ssh";
     targetSystem = system;
     sshOpts = [ ];

deployment/check/data-model-tf/nixosTest.nix

@@ -4,9 +4,10 @@
   ...
 }:
 let
+  inherit (import ./constants.nix) pathToRoot pathFromRoot;
   inherit (pkgs) system;
   deployment-config = {
-    inherit (import ./constants.nix) pathToRoot;
+    inherit pathToRoot pathFromRoot;
     nodeName = "target";
     targetSystem = system;
     sshOpts = [ ];