refactored overlay loading indicator code

lib/services/overlay_service.dart

@@ -0,0 +1,47 @@
+import 'package:flutter/material.dart';
+
+import '../widgets/loading_notifier.dart';
+
+mixin OverlayService {
+  OverlayEntry? _overlayEntry;
+
+  Future<void> showLoadingNotifier({
+    required BuildContext context,
+    required String message,
+    required VoidCallback onDismiss,
+  }) async {
+    if (_overlayEntry != null) return;
+
+    final overlayState = Overlay.of(context);
+    _overlayEntry = OverlayEntry(
+      builder: (context) => Positioned(
+        bottom: 85,
+        left: 0,
+        right: 0,
+        child: Center(
+          child: LoadingNotifier(
+            message: message,
+            onDismissed: () {
+              onDismiss();
+              removeLoadingNotifier();
+            },
+          ),
+        ),
+      ),
+    );
+
+    overlayState.insert(_overlayEntry!);
+    // overlayState.setState(() {});
+  }
+
+  void removeLoadingNotifier() {
+    if (_overlayEntry != null) {
+      _overlayEntry?.remove();
+      _overlayEntry = null;
+    }
+  }
+
+  void dispose() {
+    removeLoadingNotifier();
+  }
+}