message: Remove assumption of updated wallet being returned
  (after incrementing; this would only happen in Postgres)
diff: @@ -23,12 +23,11 @@ module.exports.addWalletBalance = function addWalletBalance () {
  const cardId = req.body.paymentId
  const card = cardId ? await CardModel.findOne({ where: { id: cardId, UserId: req.body.UserId } }) : null
  if (card) {
  - const wallet = await WalletModel.increment({ balance: req.body.balance }, { where: { UserId: req.body.UserId } })
  - if (wallet) {
  - res.status(200).json({ status: 'success', data: wallet.balance })
  - } else {
  + WalletModel.increment({ balance: req.body.balance }, { where: { UserId: req.body.UserId } }).then(() => {
  + res.status(200).json({ status: 'success', data: req.body.balance })
  + }).catch(() => {
  res.status(404).json({ status: 'error' })
  - }
  + })
  } else {
  res.status(402).json({ status: 'error', message: 'Payment not accepted.' })
  }
  