Depending on the kind of config error being shown, different "go back"
links may be more appropriate.
We probably hard-coded /login/ for it, because these config errors are
most commonly used for authentication backend config error, where it
makes sense to have /login/ as "go back", because the user most likely
indeed got there from the login page.
However, for remote_billing_bouncer_not_configured, it doesn't make
sense, because the user almost surely is already logged in and got there
by clicking "Plan management" inside the gear menu in the logged in app.
Just shows a config error page if the bouncer is not enabled. Uses a new
endpoint for this so that it can work nicely for both browser and
desktop app clients.
It's necessary, because the desktop app expects to get a json response
with either an error or billing_access_url to redirect to. Showing a
nice config error page can't be done via the json error mechanism, so
instead we just serve a redirect to the new error page, which the app
will open in the browser in a new window or tab.
Mateusz Mandera
Alex Vandiver