Support custom Firebase storage bucket

flutter_cache_manager_firebase/README.md

@@ -6,9 +6,16 @@ A Firebase implementation for [flutter_cache_manager](https://pub.dev/packages/f
 
 This library contains FirebaseCacheManager and FirebaseHttpFileService.
 
-You can easily fetch a file stored on Firebase with 
+You can easily fetch a file stored on Firebase with
 ```dart
 var file = await FirebaseCacheManager().getSingleFile(url);
 ```
 
-You could also write your own CacheManager which uses the FirebaseHttpFileService.
+You could also write your own CacheManager which uses the FirebaseHttpFileService.
+
+### Custom Firebase storage bucket
+
+You can use a custom bucket by passing `bucket` parameter. For example:
+```dart
+FirebaseCacheManager(bucket: "my-bucket");
+```

flutter_cache_manager_firebase/lib/src/firebase_cache_manager.dart

@@ -8,18 +8,21 @@ import 'firebase_http_file_service.dart';
 class FirebaseCacheManager extends CacheManager {
   static const key = 'firebaseCache';
 
-  static final FirebaseCacheManager _instance = FirebaseCacheManager._(null);
+  static final FirebaseCacheManager _instance =
+      FirebaseCacheManager._(retryOptions: retryOptions, bucket: bucket);
 
-  final RetryOptions? retryOptions;
+  static RetryOptions? retryOptions;
 
-  factory FirebaseCacheManager() {
+  static String? bucket;
+
+  factory FirebaseCacheManager({RetryOptions? retryOptions, String? bucket}) {
+    bucket = bucket;
+    retryOptions = retryOptions;
     return _instance;
   }
 
-  FirebaseCacheManager.retry({this.retryOptions = const RetryOptions()})
+  FirebaseCacheManager._({RetryOptions? retryOptions, String? bucket})
       : super(Config(key,
-            fileService: FirebaseHttpFileService(retryOptions: retryOptions)));
-
-  FirebaseCacheManager._(this.retryOptions)
-      : super(Config(key, fileService: FirebaseHttpFileService()));
+            fileService: FirebaseHttpFileService(
+                retryOptions: retryOptions, bucket: bucket)));
 }

flutter_cache_manager_firebase/lib/src/firebase_http_file_service.dart

@@ -10,12 +10,21 @@ class FirebaseHttpFileService extends HttpFileService {
 
   FirebaseHttpFileService({
     this.retryOptions,
-  });
+    this.bucket,
+  }) : super();
+
+  final String? bucket;
 
   @override
   Future<FileServiceResponse> get(String url,
       {Map<String, String>? headers}) async {
-    var ref = FirebaseStorage.instance.ref().child(url);
+    late Reference ref;
+    if (bucket != null) {
+      ref =
+          FirebaseStorage.instanceFor(bucket: "gs://$bucket").ref().child(url);
+    } else {
+      ref = FirebaseStorage.instance.ref().child(url);
+    }
 
     String downloadUrl;
     if (retryOptions != null) {