This sets the mime part's content type to type$. In the absence of a mime type and if needed by the
protocol specifications, a default mime type is determined by the context:
- – If set as a custom header, use this value.
- – application/form-data for an HTTP form post.
- – If a remote file name is set, the mime type is taken from the file name extension, or application/octet-stream by default.
- – For a multipart part, multipart/mixed.
- – text/plain in other cases.
Mime parts are created using mime:AddPart().