Yes, and you send your request while this is waiting to detect the request. Bubble, if possible, will parse the request. You will have the list of field.

But again, from what I understand of your request, you will not be able to save the file this way. Bubble expect an URL or a base64 in a json object formatted like

{
 filename: String
 contents: Base64-encoded binary data
 private: Boolean
 attach_to: String
}