Files upload with same name

**Describe the bug**
File upload with same name(in same directory) doesn't return conflict error

**To Reproduce**
Steps to reproduce the behavior:
1. Go to the app
2. Upload a file named xyz
3. Upload another file named xyz with different content
4. Doesn't return error and the file is not replaced either.

**Expected behavior**
Backend returns conflict error for the files.
Files upload is a batch operation and if there is conflict error for some files the upload returns all the entries for files and there status whether it got uploaded successfully or failed. UI needs to check the response.
The best way will be
1. Call check-upload API before uploading and inform user about the conflicting files to re- add files while uploading.
2. Check the response of the upload and inform about the failed files while uploading

Start by reproducing the duplicate-name upload in the app, then inspect the check-upload API and the upload response described in the issue. Confirm how conflicts are reported for batch entries and what status the UI receives; done means duplicate files return a conflict outcome and the UI informs the user about failed files.

Written by the indexing model from the issue text.