common: add defer function

[josephjclark]

defer is like fn, but it waits for n SECONDS before executing

defer(durationInSeconds, fn)

Where fn is any operation

Seconds because ms is unlikely to be useful, and you can always to 0.1s. Usually JS timeouts are in ms so this might catch people out and we need to be very clear.

The implementation is like:

const defer = (durationInSections, fn) => state => {
  return new Promise((resolve) => {
    setTimeout(() => {
      fn(state)
    }, 1000 * durationInSeconds)
  });
}

You can do this in job code today but it's a bit gnarly, and it feels like a useful pattern to support.

You can compose with each nicely:

each(
  '$.patients[*]',
  defer(5, post('/patients', $.data))
)