dev: update deleteUser to use FS provider

The previous implementation of deleteUser was hard-coded to use the
PuterFSProvider file system type's storage implementation specifically,
even if a different filesystem type is mounted as root or for a
particular user.

This change was tested by creating a user, adding some fsentries, and
then deleting that user. The following classes of filesystem entry were
checked:
- [x] user created directory (with contents)
  - [x] directory fsentry was deleted
- [x] user created directory (empty)
  - [x] directory fsentry was deleted
- [x] immutable directory
  - [x] directory fsentry was deleted
- [x] user created file
  - [x] file fsentry was deleted
  - [x] file storage was deleted
- [x] user created file in trash
  - [x] file fsentry was deleted
  - [x] file storage was deleted

src/backend/src/helpers.js

@@ -1151,17 +1151,12 @@ async function deleteUser(user_id){
         // delete all files from S3
         if(files !== null && files.length > 0){
             for(let i=0; i<files.length; i++){
-                // init S3 SDK
-                const svc_fs = Context.get('services').get('filesystem');
-                const svc_mountpoint =
-                    Context.get('services').get('mountpoint');
-                // NB: We use a hard-coded string to avoid circular dependency.
-                // 
-                // TODO (xiaochen): what if the provider is not PuterFSProvider?
-                const storage = svc_mountpoint.get_storage('PuterFSProvider');
-                const op_delete = storage.create_delete();
-                await op_delete.run({
-                    node: await svc_fs.node(new NodeUIDSelector(files[i].uuid))
+                const node = await svc_fs.node(new NodeUIDSelector(files[i].uuid));
+                
+                await node.provider.unlink({
+                    context: Context.get(),
+                    override_immutable: true,
+                    node,
                 });
             }
         }

src/backend/src/modules/puterfs/lib/PuterFSProvider.js

@@ -409,13 +409,13 @@ class PuterFSProvider extends putility.AdvancedBase {
         return node;
     }
 
-    async unlink({ context, node }) {
+    async unlink({ context, node, options = {} }) {
         if ( await node.get('type') === TYPE_DIRECTORY ) {
             console.log(`\x1B[31;1m===N=====${await node.get('path')}=========\x1B[0m`);
             throw new APIError(409, 'Cannot unlink a directory.');
         }
 
-        await this.#rmnode({ context, node });
+        await this.#rmnode({ context, node, options });
     }
 
     async rmdir({ context, node, options = {} }) {
@@ -442,12 +442,12 @@ class PuterFSProvider extends putility.AdvancedBase {
         await this.#rmnode({ context, node, options });
     }
 
-    async #rmnode({ node, options: _options }) {
+    async #rmnode({ node, options }) {
         // Services
         const svc_size = this.#services.get('sizeService');
         const svc_fsEntry = this.#services.get('fsEntryService');
 
-        if ( await node.get('immutable') ) {
+        if ( ! options.override_immutable && await node.get('immutable') ) {
             throw new APIError(403, 'File is immutable.');
         }