title: Flutter rounded appbar with color line
body: <p>i have a rounded Appbar with a color line. <a href="https://i.stack.imgur.com/bQHP6.png" rel="nofollow noreferrer">Here is a Screenshot.</a>
  I want the color line to follow the rounding. Is this possible, since I have not found anything about it?</p>
  <p>This is my code so far:</p>
  <pre><code>class LoginPage extends StatelessWidget {
    @override
    Widget build(BuildContext context) {
      return Scaffold(
        appBar: AppBar(
          title: Text(
            &quot;Test&quot;,
            style: TextStyle(fontStyle: FontStyle.italic),
          ),
          centerTitle: true,
          elevation: 10,
          backgroundColor: Colors.cyan[900],
          bottom: PreferredSize(
              preferredSize: Size.fromHeight(4.0),
              child: SizedBox(
                height: 5,
                child: Container(
                  color: Colors.orange,
                ),
              )),
          shadowColor: Colors.cyan[900],
          shape: RoundedRectangleBorder(
            borderRadius: BorderRadius.vertical(
              bottom: Radius.circular(30),
            ),
          ),
        ),
      );
    }
  }
  </code></pre>