rbw: add module (#1998)

`rbw` is a stand-alone Bitwarden client, which makes use of a daemon to
cache your password and manage state.

Its configuration can be managed by `home-manager` or not, leaving the
user free to configure it through `rbw config`.

tests/modules/programs/rbw/settings.nix

@@ -0,0 +1,39 @@
+{ pkgs, ... }:
+let
+  inherit (pkgs.stdenv.hostPlatform) isDarwin;
+
+  path = if isDarwin then
+    "Library/Application Support/rbw/config.json"
+  else
+    ".config/rbw/config.json";
+
+  expected = pkgs.writeText "rbw-expected.json" ''
+    {
+      "base_url": "bitwarden.example.com",
+      "email": "name@example.com",
+      "identity_url": "identity.example.com",
+      "lock_timeout": 300,
+      "pinentry": "@pinentry-gnome3@/bin/pinentry"
+    }
+  '';
+in {
+  config = {
+    programs.rbw = {
+      enable = true;
+      settings = {
+        email = "name@example.com";
+        base_url = "bitwarden.example.com";
+        identity_url = "identity.example.com";
+        lock_timeout = 300;
+        pinentry = "gnome3";
+      };
+    };
+
+    nixpkgs.overlays = [ (import ./overlay.nix) ];
+
+    nmt.script = ''
+      assertFileExists home-files/${path}
+      assertFileContent home-files/${path} '${expected}'
+    '';
+  };
+}