modules/mavlink-router: include custom version of gitIni settings format

The upstream gitIni quotes strings now, which is not compatible with
mavlink-router.

modules/services/networking/mavlink-router.nix

@@ -1,17 +1,54 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, pkgs, ... }: let
+  cfg = config.services.mavlink-router;
 
-with lib;
+  # Based on lib.generators.toGitINI, but without quoting of subsection headers
+  # and string values.
+  toConf = attrs:
+    let
+      mkSectionName = name:
+        let
+          sections = lib.strings.splitString "." name;
+          section = builtins.head sections;
+          subsections = builtins.tail sections;
+          subsection = lib.concatStringsSep "." subsections;
+        in if subsections == [ ]
+        then name
+        else "${section} ${subsection}";
 
-let
-  cfg = config.services.mavlink-router;
-  settingsFormat = pkgs.formats.gitIni { };
+      # generation for multiple ini values
+      mkKeyValue = k: v:
+        let mkKeyValue = lib.generators.mkKeyValueDefault { } " = " k;
+        in lib.concatStringsSep "\n" (builtins.map (kv: "\t" + mkKeyValue kv) (lib.toList v));
+
+      # converts { a.b.c = 5; } to { "a.b".c = 5; } for toINI
+      flattenAttrs = let
+        recurse = path: value:
+          if builtins.isAttrs value && !lib.isDerivation value then
+            lib.mapAttrsToList (name: value: recurse ([ name ] ++ path) value) value
+          else if builtins.length path > 1 then {
+            ${lib.concatStringsSep "." (lib.reverseList (builtins.tail path))}.${builtins.head path} = value;
+          } else {
+            ${builtins.head path} = value;
+          };
+      in attrs: lib.foldl lib.recursiveUpdate { } (lib.flatten (recurse [ ] attrs));
+
+      toINI_ = lib.generators.toINI { inherit mkKeyValue mkSectionName; };
+    in
+      toINI_ (flattenAttrs attrs);
+
+  settingsFormat = {
+    type = with lib.types; let
+      iniAtom = (pkgs.formats.ini { }).type/*attrsOf*/.functor.wrapped/*attrsOf*/.functor.wrapped;
+    in attrsOf (attrsOf (either iniAtom (attrsOf iniAtom)));
+    generate = name: value: pkgs.writeText name (toConf value);
+  };
 in {
   # Interface
 
   options.services.mavlink-router = {
-    enable = mkEnableOption "MAVLink Router";
+    enable = lib.mkEnableOption "MAVLink Router";
 
-    settings = mkOption {
+    settings = lib.mkOption {
       type = settingsFormat.type;
       default = {};
       example = {
@@ -29,7 +66,7 @@ in {
 
   # Implementation
 
-  config = mkIf cfg.enable {
+  config = lib.mkIf cfg.enable {
     systemd.packages = [ pkgs.mavlink-router ];
 
     systemd.services.mavlink-router = {