add support for creating rooms

Fixes #81

lib/helpers/extensions/with_progress_snackbar.dart

@@ -0,0 +1,37 @@
+import "package:material_ui/material_ui.dart";
+
+extension WithProgressSnackbar on BuildContext {
+  /// Shows [progress] in a snackbar while [action] runs, and shows any error
+  /// it throws in an error snackbar.
+  ///
+  /// Returns the result of [action], or null if it failed.
+  Future<T?> withProgressSnackbar<T>(
+    String progress,
+    Future<T> Function() action,
+  ) async {
+    final messenger = ScaffoldMessenger.of(this);
+    final colorScheme = Theme.of(this).colorScheme;
+
+    final snackbar = messenger.showSnackBar(
+      .new(content: Text(progress), duration: const .new(days: 1)),
+    );
+
+    try {
+      return await action();
+    } catch (error) {
+      messenger.showSnackBar(
+        .new(
+          backgroundColor: colorScheme.errorContainer,
+          content: Text(
+            error.toString(),
+            style: .new(color: colorScheme.onErrorContainer),
+          ),
+        ),
+      );
+
+      return null;
+    } finally {
+      snackbar.close();
+    }
+  }
+}