move new packages to pkgs/default.nix

pkgs/service-fns/default.nix

@@ -0,0 +1,10 @@
+{writeText}:
+writeText "service-fns.sh" ''
+  output() { cat $1/.outputs/$2; }
+  output_path() { echo $(realpath $1/.outputs)/$2; }
+  mkoutputs() {
+    d=/run/service-state/$1
+    mkdir -m 2750 -p $d && chown root:system $d
+    echo $d
+  }
+''