This unexported function exists to catch tokens that are technically valid, i.e. `inherits(token, "Token2.0")` is TRUE, but that have dysfunctional credentials.
is_legit_token(x)
Other authentication functions: gar_attach_auto_auth,
gar_auth_service, gar_auth,
gar_auto_auth, gar_gce_auth,
get_google_token,
token_exists