feat: Allow subclassing Endpoints (serverpod#3404)

Author: tp

packages/serverpod/lib/serverpod.dart

@@ -4,6 +4,9 @@
 // See: https://github.com/serverpod/serverpod/pull/2900
 library serverpod;
 
+// Annotations
+export 'package:serverpod_shared/src/annotations.dart';
+
 // Config
 export 'package:serverpod_shared/src/config.dart';
 

packages/serverpod/lib/src/cloud_storage/public_endpoint.dart

@@ -4,7 +4,6 @@ import 'dart:typed_data';
 import 'package:path/path.dart' as p;
 import 'package:serverpod/serverpod.dart';
 import 'package:serverpod/src/generated/cloud_storage_direct_upload.dart';
-import 'package:serverpod_shared/annotations.dart';
 
 const _endpointName = 'serverpod_cloud_storage';