I'm not currently part of a professional team, but it seems that StackOverflow Channels will be a great fit for this. It's a private Q&A space for teams. It's free while in Early Access, and they've stated on the StackOverflow podcast that they intend to keep it free for teams upto a certain size.
We're a place where coders share, stay up-to-date and grow their careers.
We strive for transparency and don't collect excess data.