For certain token flows, the
"https://www.googleapis.com/auth/userinfo.email" scope is unconditionally
included. This grants permission to retrieve the email address associated
with a token; gargle uses this to index cached OAuth tokens. This grants no
permission to view or send email. It is considered a low value scope and
does not appear on the consent screen.
path
JSON identifying the service account, in one of the forms
supported for the txt argument of jsonlite::fromJSON() (typically, a
file path or JSON string).
...
Additional arguments passed to all credential functions.