Debug & Fix Rclone FileLu Backend to Pass All Integration Tests (go test -v -short ./backend/filelu)

Budget: $300
Fix Rclone FileLu Backend to Pass All Integration Tests (go test -v -short ./backend/filelu)
I'm working on a custom backend for Rclone that integrates with FileLu Cloud Storage https://github.com/kingston125/rclone.
The backend is mostly complete, but several integration tests are still failing.

Your task is to review and fix the Go backend code to make all the failing tests pass.

Run the test command: go test -v -short ./backend/filelu
The following tests currently FAIL and need to be PASSED:
--- FAIL: TestIntegration/FsMkdir/FsMkdirRmdirSubdir (8.93s)
--- FAIL: TestIntegration/FsMkdir/FsListDirNotFound (0.32s)
--- FAIL: TestIntegration/FsMkdir/FsPutZeroLength (1.33s)
--- FAIL: TestIntegration/FsMkdir/FsPutFiles (10.14s)
--- FAIL: TestIntegration/FsMkdir/FsUploadUnknownSize (8.01s)
--- FAIL: TestIntegration/FsMkdir/FsUploadUnknownSize/FsUpdateUnknownSize (5.33s)

You will need to review the backend implementation and ensure the code works with Rclone’s expectations for behavior — including correctly handling zero-length files, file updates, folder structures (including empty subfolders), and error reporting.

I will provide:
The current filelu backend source code here: https://github.com/kingston125/rclone/tree/master/backend/filelu
Access to FileLu Rclone key for testing (you can register an account at https://filelu.com/account/ and get your Rclone key) or you can ask me via chat I will provide one.


Requirements:
Strong knowledge of Go (Golang)
Familiarity with Rclone’s backend/plugin structure
Experience with REST APIs and JSON decoding
Comfortable working with file system operations and nested directories
Can debug and fix failing integration tests in Go

Deliverables:
Updated filelu backend in rclone
All tests pass using:
go test -v -short ./backend/filelu