Upgrade flutter_lints dependency. Lint code according to the use_string_in_part_of_directives rule.

lib/src/common/medium_type.dart

@@ -1,4 +1,4 @@
-part of photogallery;
+part of '../../photo_gallery.dart';
 
 /// A medium type.
 enum MediumType {

lib/src/image_providers/album_thumbnail_provider.dart

@@ -1,4 +1,4 @@
-part of photogallery;
+part of '../../photo_gallery.dart';
 
 /// Fetches the given album thumbnail from the gallery.
 class AlbumThumbnailProvider extends ImageProvider<AlbumThumbnailProvider> {

lib/src/image_providers/photo_provider.dart

@@ -1,4 +1,4 @@
-part of photogallery;
+part of '../../photo_gallery.dart';
 
 /// Fetches the given image from the gallery.
 class PhotoProvider extends ImageProvider<PhotoProvider> {

lib/src/image_providers/thumbnail_provider.dart

@@ -1,4 +1,4 @@
-part of photogallery;
+part of '../../photo_gallery.dart';
 
 /// Fetches the given medium thumbnail from the gallery.
 class ThumbnailProvider extends ImageProvider<ThumbnailProvider> {

lib/src/models/album.dart

@@ -1,4 +1,4 @@
-part of photogallery;
+part of '../../photo_gallery.dart';
 
 /// A album in the gallery.
 @immutable

lib/src/models/media_page.dart

@@ -1,4 +1,4 @@
-part of photogallery;
+part of '../../photo_gallery.dart';
 
 /// A list of media with pagination support.
 @immutable

lib/src/models/medium.dart

@@ -1,4 +1,4 @@
-part of photogallery;
+part of '../../photo_gallery.dart';
 
 /// A medium in the gallery.
 ///

pubspec.yaml

@@ -20,7 +20,7 @@ dev_dependencies:
   # activated in the `analysis_options.yaml` file located at the root of your
   # package. See that file for information about deactivating specific lint
   # rules and activating additional ones.
-  flutter_lints: ^2.0.0
+  flutter_lints: ^3.0.0
 
 # For information on the generic Dart part of this file, see the
 # following page: https://dart.dev/tools/pub/pubspec