/api/remove_matadata endpoint fails when multipart body is streamed

When requesting to endpoint /api/remove_metadata without Content-Length HTTP header, the API returns 400 with message "No file part", even though the body exists and is encoded correctly.

Request without Content-Length is a valid http request when using chunked transfer encoding (Wikipedia, MDN). Such method is useful when streaming file from network/disk directly without loading the entire file to memory (and thus the client making the api request not aware of the file size).

Reproducable in Docker (built with production Dockerfile).

Wireshark capture of failing request:

Succeeding request: