Milestone: successful Plaid integration

I got my Plaid integration working today! It's just to /accounts/balance/get but it completed end-to-end.

Note: if you're working with Plaid API and have "limited production access", you will have to configure your "Data Transparency" settings in your Plaid dashboard before you're able to link a real bank account. FYI I was stuck on that for a while and couldn't figure out what was wrong!