Pass auth_url param through to oauth_flow_device

[taerwin]

auth_url is not passed through to oauth_device_flow see issue #120

[hadley]

Could you please explain why you want this?

[taerwin]

There is currently no way to set auth_url in req_oath_device() directly or via auth_params. Ticket suggests it should be able to be set as follows:

req %>%
httr2::req_oauth_device(
client = cl,
auth_url = "http://xyz/oauth2/authorize",
cache_disk = TRUE
) %>%
httr2::req_perform()

This patch adds auth_url as a param and also sets this param to be passed through to oauth_flow_device

[hadley]

Ah, got it.