Use more contextual knowledge re: oob auth

[jennybc]

I could make the default logic for oob auth a bit more humane.

For example, we could determine that we are on RStudio Server and use oob auth, w/o having to receive explicit instructions via the option or arg.

How to tell?

rstudioapi::versionInfo()$mode
[1] "server"

Also, since I'm here, let me record other ways I know of learning more about context: The env var R_CONFIG_ACTIVE is "shiny" on shinyapps.io and "rstudio_cloud" on RStudio Cloud.

When you're in RStudio, you can call RStudio.Version(). But that's a function attached by RStudio itself and would presumably require weird gymnastics in a CRAN package.

RStudio v1.3 will set RSTUDIO_PROGRAM_MODE.

RSTUDIO_HTTP_REFERER is set in RStudio Servier but not in Desktop.

[jennybc]

Maybe gargle should consider the option httr_oob_default? If someone has bothered to set that, it seems a better fallback than FALSE.

[jennybc]

The more I think about this, the more I think most of it belongs in httr(2), not here.