$refresh()) when access expires.oauth2.0_token(endpoint, app, scope = NULL, type = NULL,
  use_oob = getOption("httr_oob_default"), as_header = TRUE,
  cache = getOption("httr_oauth_cache"))TRUE, the default, sends oauth in bearer header.
If FALSE, adds as parameter to url.oauth_endpointoauth_app"httr_oob_default" default.TRUE means to cache
using the default cache file .oauth-httr, FALSE means
don't cache, and NA means to guess using some sensible heuristics.
A string mean use the specified pToken2.0 reference class (RC) object.Token for full details about the token object, and the
caching policies used to store credentials across sessions.oauth1.0_token;
  oauth_app; oauth_endpoint