### What?
The browser was incorrectly setting the mimetype for `.glb` and `.gltf`
files to `application/octet-stream` when uploading when they should be
receiving proper types consistent with `glb` and `gltf`.
This patch adds logic to infer the correct `MIME` type for `.glb` files
(`model/gltf-binary`) & `gltf` files (`model/gltf+json`) based on file
extension during multipart processing, ensuring consistent MIME type
detection regardless of browser behavior.
Fixes#12620
05eeddba7c
