[signup] Handle duplicate key error

[22shubh22]

Actual:- 400 Bad request obtained without any error message.
Expected:- The case should be considered and the message should be displayed.

todo-api-design/src/utils/auth.js

Lines 23 to 30 in ff91497

	try {
	const user = await User.create(req.body)
	const token = newToken(user)
	return res.status(201).send({ token })
	} catch (e) {
	console.error(e)
	return res.status(400).end()
	}