Authenticate using a refresh token, following the process described in
Section 6 of RFC 6749.
This technique is primarily useful for testing: you can manually retrieve
a OAuth token using another OAuth flow (e.g. with oauth_flow_auth_code()
),
extract the refresh token from the result, and then save in an environment
variable for use in automated tests.
When requesting an access token, the server may also return a new refresh
token. If this happens, oauth_flow_refresh()
will warn, and you'll have
retrieve a new update refresh token and update the stored value. If you find
this happening a lot, it's a sign that you should be using a different flow
in your automated tests.
Learn more about the overall OAuth authentication flow in vignette("oauth")
.