[BUG] `UploadedPart` is unserializable/constructable therefore cannot be passed to MultipartUpload::complete in a subsequent request

[lwansbrough]

Is there an existing issue for this?

• [X] I have searched the existing issues

What version of workers-rs are you using?

0.0.15

Describe the bug

Because MultipartUpload::complete requires instances of UploadedPart, we need to be able to construct or deserialize the UploadedPart iterable list from the request body. Ideally a method would be available to pass the request or its body directly to a constructor to avoid having to manage deserialization in my worker code. Multipart uploads to R2 do not appear to be supported until this is fixed.

Steps To Reproduce

No response

[lwansbrough]

If I can do let uploaded_parts = req.json::<Vec<UploadedPart>>().await?; then we really just need UploadedPart to be de/ser.