Implemented EXIF store and display (#19)

* Added EXIF extracting in the backend
* Added EXIF displaying on `image_viewer_page.dart`
* Added Icon for backup option not enable

mobile/lib/modules/asset_viewer/models/image_viewer_page_state.model.dart

@@ -0,0 +1,45 @@
+import 'dart:convert';
+
+class ImageViewerPageState {
+  final bool isBottomSheetEnable;
+  ImageViewerPageState({
+    required this.isBottomSheetEnable,
+  });
+
+  ImageViewerPageState copyWith({
+    bool? isBottomSheetEnable,
+  }) {
+    return ImageViewerPageState(
+      isBottomSheetEnable: isBottomSheetEnable ?? this.isBottomSheetEnable,
+    );
+  }
+
+  Map<String, dynamic> toMap() {
+    return {
+      'isBottomSheetEnable': isBottomSheetEnable,
+    };
+  }
+
+  factory ImageViewerPageState.fromMap(Map<String, dynamic> map) {
+    return ImageViewerPageState(
+      isBottomSheetEnable: map['isBottomSheetEnable'] ?? false,
+    );
+  }
+
+  String toJson() => json.encode(toMap());
+
+  factory ImageViewerPageState.fromJson(String source) => ImageViewerPageState.fromMap(json.decode(source));
+
+  @override
+  String toString() => 'ImageViewerPageState(isBottomSheetEnable: $isBottomSheetEnable)';
+
+  @override
+  bool operator ==(Object other) {
+    if (identical(this, other)) return true;
+
+    return other is ImageViewerPageState && other.isBottomSheetEnable == isBottomSheetEnable;
+  }
+
+  @override
+  int get hashCode => isBottomSheetEnable.hashCode;
+}