The control panel on the Google side doesn't seem to match the
instructions we have; it looks pretty 2017 to me, so I imagine
it's had a redesign since the instructions were written.
Also, in dev, EXTERNAL_HOST is now a port on zulipdev.com, not on
localhost.
Update these instructions for those developments, and edit lightly.
In dev, recommend setting in `dev_settings` instead of in
`prod_settings_template`; that feels to me a little more reflective of
the actual intent, and the effect should be equivalent.
In some minutes of searching yesterday afternoon on the docs site,
I couldn't find docs on how to set up our OAuth integrations for
the dev environment -- even though I was pretty sure they should
be there somewhere, because I'd just been told that. Wasn't until
I considered the problem fresh today, and grepped the docs source
instead, that I found them.
So, move them to a separate page so they're in the nav.
Greg Price