308 Redirect plus multipart/form-data causes wrong boundary

Reproduction

Steps to reproduce the behavior:

1. Fetch an API on some endpoint (for example /something), sending a file as form-data (during my testing, the content were irrelevant)
2. Make the API redirect the client to /something/ using a 308 permanent redirect
3. Watch the API not being able to fetch the file due to an invalid request

Expected behavior

The Client sends the same request twice. But instead the client sends the same headers (including the boundary definition), but a different boundary in the body.

Screenshots

(don't worry, the JWT does not contain any relevant data)

Your Environment

software	version
node-fetch	n/a (builtin)
node	22.8.0-bookworm (docker)
npm	10.8.2
Operating System	Docker amd64

Additional context