feat: Filter userdata.json input so we don't pass undefined items

flake.nix

@@ -25,9 +25,32 @@
             deployment
             ./configuration.nix
             selfprivacy-api.nixosModules.default
-            {
+            (
+              let
+                deepFilter = ref: attrset:
+                  builtins.foldl'
+                    (acc: key:
+                      if builtins.hasAttr key ref then
+                        let
+                          value = attrset.${key};
+                          refValue = ref.${key};
+                        in
+                        acc // {
+                          ${key} =
+                            if builtins.isAttrs value && builtins.isAttrs refValue then
+                              deepFilter refValue value
+                            else
+                              value;
+                        }
+                      else
+                        acc
+                    )
+                    { }
+                    (builtins.attrNames attrset);
+              in
+              { options, ... }: {
                 # pass userdata (parsed from JSON) options to selfprivacy module
-              selfprivacy = userdata;
+                selfprivacy = deepFilter options.selfprivacy userdata;
 
                 # embed top-level flake source folder into the build
                 environment.etc."selfprivacy/nixos-config-source".source =
@@ -47,6 +70,7 @@
                   cp -r --no-preserve=all ${top-level-flake}/ -T /etc/nixos/
                 '';
               }
+            )
           ]
           ++
           # add SP modules, but constrain available config attributes for each