Improve login route

lib/ui/widgets/login_scaffold.dart

@@ -0,0 +1,57 @@
+import 'package:comunic/utils/intl_utils.dart';
+import 'package:flutter/material.dart';
+
+/// Custom "Scaffold" for signed out users
+///
+/// @author Pierre Hubert
+
+class LoginScaffold extends StatelessWidget {
+  final Widget child;
+
+  const LoginScaffold({Key key, @required this.child})
+      : assert(child != null),
+        super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    final mediaQuery = MediaQuery.of(context);
+
+    final availableHeight =
+        mediaQuery.size.height - mediaQuery.viewInsets.bottom;
+    final minHeight = 400.0;
+
+    final contentHeight =
+        availableHeight < minHeight ? minHeight : availableHeight;
+
+    return Scaffold(
+      body: SingleChildScrollView(
+        child: Center(
+          child: Container(
+            height: contentHeight,
+            child: ConstrainedBox(
+              constraints: BoxConstraints(maxWidth: 300),
+              child: Column(
+                children: <Widget>[
+                  Spacer(flex: 3),
+                  Text("Comunic", style: TextStyle(fontSize: 50)),
+                  Spacer(flex: 1),
+                  Text(tr("Free social network that respect your privacy")),
+                  Spacer(flex: 1),
+                  Padding(
+                    padding: const EdgeInsets.all(8.0),
+                    child: Material(
+                      child: child,
+                      color: Colors.indigo.shade500,
+                    ),
+                  ),
+                  Spacer(flex: 5),
+                ],
+              ),
+            ),
+          ),
+        ),
+      ),
+      backgroundColor: Colors.indigo.shade900,
+    );
+  }
+}