Asks Subbly to email the customer when a product or a survey answer is back in
stock. Watch for `stockCount: 0` on a variant, a plan or an answer, and offer
the alert there.
The shop must turn alerts on: `shop.settings.outOfStockEnabled` and
`shop.limits.outOfStock` must both be `true`.
What to watch, and where to send the alert.
Address the alert goes to.
The variant or plan that ran out. Send this or `answerId`, not both.
The survey answer that ran out. Send this or `productId`, not both.
How many units the customer wants.
The alert record.
ID of the record.
The shop the record belongs to.
The product being watched.
Address the alert goes to.
How many units the customer wants.
ID of the watched product or survey answer.
What is being watched.
When the item came back in stock. Empty until it does.
When the record was created.
When the record last changed.
```js title="Watch a variant"
await subbly.stock.subscribe({
email: 'me@example.com',
productId: 456,
quantity: 1
})
```
```js title="Watch a survey answer"
await subbly.stock.subscribe({
email: 'me@example.com',
answerId: 789
})
```