satty: add satty to program modules

Add satty, a wlroots based screenshot annotation tool, to the programs
module.

tests/modules/programs/satty/basic-configuration.nix

@@ -0,0 +1,26 @@
+{
+  programs.satty = {
+    enable = true;
+    settings = {
+      general = {
+        fullscreen = true;
+        corner-roundness = 12;
+        initial-tool = "brush";
+        output-filename = "/tmp/test.png";
+      };
+
+      font.family = "Roboto";
+
+      color-palette.palette = [ "#00ffff" ];
+    };
+  };
+
+  nmt.script =
+    let
+      configFile = "home-files/.config/satty/config.toml";
+    in
+    ''
+      assertFileExists "${configFile}"
+      assertFileContent "${configFile}" ${./expected-config.toml}
+    '';
+}

tests/modules/programs/satty/default.nix

@@ -0,0 +1,6 @@
+{ lib, pkgs, ... }:
+
+lib.optionalAttrs pkgs.stdenv.hostPlatform.isLinux {
+  satty-basic-configuration = ./basic-configuration.nix;
+  satty-empty-configuration = ./empty-settings.nix;
+}

tests/modules/programs/satty/empty-settings.nix

@@ -0,0 +1,7 @@
+{
+  programs.satty.enable = false;
+
+  nmt.script = ''
+    assertPathNotExists "home-files/.config/satty"
+  '';
+}

tests/modules/programs/satty/expected-config.toml

@@ -0,0 +1,11 @@
+[color-palette]
+palette = ["#00ffff"]
+
+[font]
+family = "Roboto"
+
+[general]
+corner-roundness = 12
+fullscreen = true
+initial-tool = "brush"
+output-filename = "/tmp/test.png"