code: @SuppressWarnings("WeakerAccess")
      public Request<UserProfile, AuthenticationException> userInfo(@NonNull String accessToken) {
          return profileRequest()
                  .addHeader(HEADER_AUTHORIZATION, "Bearer " + accessToken);
      }
docs: Returns the information of the user associated with the given access_token.
  Example usage:
  <pre>
  {@code
  client.userInfo("{access_token}")
  .start(new BaseCallback<UserProfile>() {
  {@literal}Override
  public void onSuccess(UserProfile payload) { }
  
  {@literal}@Override
  public void onFailure(AuthenticationException error) { }
  });
  }
  </pre>
  
  @param accessToken used to fetch it's information
  @return a request to start