nixos/gotify: init module and test

nixos/modules/services/web-apps/gotify-server.nix

@@ -0,0 +1,49 @@
+{ pkgs, lib, config, ... }:
+
+with lib;
+
+let
+  cfg = config.services.gotify;
+in {
+  options = {
+    services.gotify = {
+      enable = mkEnableOption "Gotify webserver";
+
+      port = mkOption {
+        type = types.port;
+        description = ''
+          Port the server listens to.
+        '';
+      };
+
+      stateDirectoryName = mkOption {
+        type = types.str;
+        default = "gotify-server";
+        description = ''
+          The name of the directory below <filename>/var/lib</filename> where
+          gotify stores its runtime data.
+        '';
+      };
+    };
+  };
+
+  config = mkIf cfg.enable {
+    systemd.services.gotify-server = {
+      wantedBy = [ "multi-user.target" ];
+      after = [ "network.target" ];
+      description = "Simple server for sending and receiving messages";
+
+      environment = {
+        GOTIFY_SERVER_PORT = toString cfg.port;
+      };
+
+      serviceConfig = {
+        WorkingDirectory = "/var/lib/${cfg.stateDirectoryName}";
+        StateDirectory = cfg.stateDirectoryName;
+        Restart = "always";
+        DynamicUser = "yes";
+        ExecStart = "${pkgs.gotify-server}/bin/server";
+      };
+    };
+  };
+}