Plaid Upload transfer diligence document on behalf of the originator

Third-party sender customers can use `/transfer/diligence/document/upload` endpoint to upload a document on behalf of its end customer (i.e. originator) to Plaid. You’ll need to send a request of type multipart/form-data. You must provide the `client_id` in the `PLAID-CLIENT-ID` header and `secret` in the `PLAID-SECRET` header.