✨ Added pi4 to systems, moved getSecret function to lib

lib/default.nix

@@ -2,8 +2,11 @@
 { lib, ... }:
 
 {
+  getSecret = with lib.strings; filePath: trim (removeSuffix "\n" (builtins.readFile filePath));
+
   # use path relative to the root of the project
   relativeToRoot = lib.path.append ../.;
+
   scanPaths =
     path:
     builtins.map (f: (path + "/${f}")) (