Send back a helpful error message object if an error occurs

[rye]

This would be a useful addition to our flow.

Currently, we do something like:

oleville-voting/routes/ballot.js

Lines 6 to 11 in 21879ce

	router.get('/', async (req, res) => {
	// check that the user requesting is logged in
	if (!req.user) {
	res.sendStatus(401) // the user is not logged in
	return
	}

Note the res.sendStatus(xxx). The docs say that we can chain a .status(code) with a .send(body) to send a custom body along.

I propose something like this as the syntax for our errors:

{
	"errors": [
		{"type": "Unauthorized", "message": "You did not specify a valid token."},
		{"type": "Unauthorized", "message": "Google said you're bad at doing stuff."}
	]
}

Minified, of course.