``validateFeedback`` checks that all of the required keys were sent in the request, so you can't send feedback without a message. If the check passes, it returns a new data object that filters out all of the keys that aren't listed in ``publicFeedbackObj``, so a request can't submit and falsify things like timestamps/usernames. (On that note, the ``user`` field really shouldn't be in ``publicFeedbackObj``. Woops.)

It's the same function as ``validateGameData`` in ``submit.js``.