Improved error messaging on malformed requests to the Members endpoint
Previously, if an object was passed as the value of the email field in a POST to the Lists/members endpoint, the server would return a 500 error. Now we return a 400 error with a clear error message.
We saw multiple occurrences of these errors in our logs. Ideally, badly formed requests shouldn’t return 500 errors, and we should give more information to callers when errors do occur.