code: public static Response post(URI uri, File file, Credentials credentials) throws URISyntaxException, HttpException {
          return postMultiPart(new HttpPost(uri), new FileBody(file), credentials, null);
      }
docs: Performs an HTTP POST on the given URL.
  Basic auth is used if credentials object is not null.
  
  @param uri         The URI to connect to.
  @param file        The file to send as MultiPartFile.
  @param credentials Instance implementing {@link Credentials} interface holding a set of credentials
  @return The HTTP response as Response object.
  @throws URISyntaxException
  @throws HttpException