Does advanced multipart support spread?

[msyyc]

According to #3046, users shall set @multipartBody explicitly for multipart, does it mean that multipart doesn't support spread? For example, will @typespec/http treat the following API as multipart API?

model MultiPartModel {
  id: HttpPart<string>;
  file: HttpPart<File>;
} 

op upload(...{...MultiPartModel, @header contentType: "multipart/form-data"})

cc @timotheeguerin @bterlson

[timotheeguerin]

yeah this wasn't part of the design, we decided multipart should only work with the explicit @multipartBody decorator(why we have a separate one from @body)