feat: add contact during call if contact is unknown

dialer/lib/features/call/call_page.dart

@@ -1,6 +1,7 @@
 import 'dart:async';
 import 'dart:typed_data';
 import 'package:flutter/material.dart';
+import 'package:flutter_contacts/flutter_contacts.dart';
 import 'package:dialer/services/call_service.dart';
 import 'package:dialer/services/obfuscate_service.dart';
 import 'package:dialer/widgets/username_color_generator.dart';
@@ -35,6 +36,8 @@ class _CallPageState extends State<CallPage> {
   StreamSubscription<String>? _callStateSubscription;
   StreamSubscription<Map<String, dynamic>>? _audioStateSubscription;
 
+  bool get isNumberUnknown => widget.displayName == widget.phoneNumber;
+
   @override
   void initState() {
     super.initState();
@@ -198,6 +201,23 @@ class _CallPageState extends State<CallPage> {
     }
   }
 
+  void _addContact() async {
+    if (await FlutterContacts.requestPermission()) {
+      final newContact = Contact()..phones = [Phone(widget.phoneNumber)];
+      final updatedContact =
+          await FlutterContacts.openExternalInsert(newContact);
+      if (updatedContact != null) {
+        ScaffoldMessenger.of(context).showSnackBar(
+          SnackBar(content: Text('Contact added successfully!')),
+        );
+      }
+    } else {
+      ScaffoldMessenger.of(context).showSnackBar(
+        SnackBar(content: Text('Permission denied for contacts')),
+      );
+    }
+  }
+
   @override
   Widget build(BuildContext context) {
     final double avatarRadius = isKeypadVisible ? 45.0 : 45.0;
@@ -416,11 +436,12 @@ class _CallPageState extends State<CallPage> {
                             Row(
                               mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                               children: [
+                                if (isNumberUnknown)
                                   Column(
                                     mainAxisSize: MainAxisSize.min,
                                     children: [
                                       IconButton(
-                                      onPressed: () {},
+                                        onPressed: _addContact,
                                         icon: const Icon(
                                           Icons.person_add,
                                           color: Colors.white,