Begin add settings

lib/widgets/pages/settings.dart

@@ -0,0 +1,47 @@
+import 'package:desktopapp/utils/mailer.dart';
+import 'package:desktopapp/widgets/pages/settings/messages_settings.dart';
+import 'package:desktopapp/widgets/pages/settings/whitelist_settings.dart';
+import 'package:flutter/material.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+
+class Settings extends StatefulWidget {
+  const Settings({Key? key}) : super(key: key);
+
+  @override
+  _SettingsState createState() => _SettingsState();
+}
+
+class _SettingsState extends State<Settings> {
+  MailerSettings? mailerSettings;
+  Widget buildContent(BuildContext context, SharedPreferences prefs) {
+    return Padding(
+      padding: const EdgeInsets.all(16.0),
+      child: GridView(
+        gridDelegate: const SliverGridDelegateWithFixedCrossAxisCount(
+            crossAxisCount: 2, mainAxisSpacing: 8.0, crossAxisSpacing: 8.0),
+        children: [
+          MessagesSettings(settings: mailerSettings!, prefs: prefs),
+          WhitelistSettings(settings: mailerSettings!, prefs: prefs)
+        ],
+      ),
+    );
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+        appBar: AppBar(title: const Text('Settings')),
+        body: FutureBuilder(
+            future: SharedPreferences.getInstance(),
+            builder: (BuildContext context,
+                AsyncSnapshot<SharedPreferences> snapshot) {
+              if (snapshot.hasData) {
+                final prefs = snapshot.data!;
+                mailerSettings = MailerSettings.loadSettings(prefs);
+                return buildContent(context, prefs);
+              } else {
+                return const Center(child: CircularProgressIndicator());
+              }
+            }));
+  }
+}