For internal use or for those programming around the trackdown API.
Returns a token pre-processed with httr::config(). Most users
do not need to handle tokens "by hand" or, even if they need some
control, trackdown_auth() is what they need. If there is no current
token, trackdown_auth() is called to either load from cache or
initiate OAuth2.0 flow.
If auth has been deactivated via trackdown_deauth(), trackdown_token()
returns NULL.
Value
A request object (an S3 class provided by httr).
See also
Other low-level API functions:
trackdown_has_token()