nixos/taskserver: Handle declarative conf via JSON

We now no longer have the stupid --service-helper option, which silences
messages about already existing organisations, users or groups.

Instead of that option, we now have a new subcommand called
"process-json", which accepts a JSON file directly from the specified
NixOS module options and creates/deletes the users accordingly.

Note that this still has a two issues left to solve in this area:

 * Deletion is not supported yet.
 * If a user is created imperatively, the next run of process-json will
   delete it once deletion is supported.

So we need to implement deletion and a way to mark organisations, users
and groups as "imperatively managed".

Signed-off-by: aszlig <aszlig@redmoonstudios.org>

nixos/modules/services/misc/taskserver/default.nix

@@ -142,8 +142,6 @@ let
     propagatedBuildInputs = [ pkgs.pythonPackages.click ];
   };
 
-  ctlcmd = "${nixos-taskserver}/bin/nixos-taskserver --service-helper";
-
   withMeta = meta: defs: mkMerge [ defs { inherit meta; } ];
 
 in {
@@ -432,20 +430,10 @@ in {
 
       environment.TASKDDATA = cfg.dataDir;
 
-      preStart = ''
-        ${concatStrings (mapAttrsToList (orgName: attrs: ''
-          ${ctlcmd} add-org ${mkShellStr orgName}
-
-          ${concatMapStrings (user: ''
-            echo Creating ${user} >&2
-            ${ctlcmd} add-user ${mkShellStr orgName} ${mkShellStr user}
-          '') attrs.users}
-
-          ${concatMapStrings (group: ''
-            ${ctlcmd} add-group ${mkShellStr orgName} ${mkShellStr user}
-          '') attrs.groups}
-        '') cfg.organisations)}
-      '';
+      preStart = let
+        jsonOrgs = builtins.toJSON cfg.organisations;
+        jsonFile = pkgs.writeText "orgs.json" jsonOrgs;
+      in "${nixos-taskserver}/bin/nixos-taskserver process-json '${jsonFile}'";
 
       serviceConfig = {
         ExecStart = "@${taskd} taskd server";