Add batching by topic for published events

[andyrichardson]

About

Resolvers should be called with an array of events (due to batching of events).

Note: Needs exploration to see if this is necessary and/or common practice

Example

Before

{
 // ...
  resolve: (event) => {
    console.log(event) // { topic: 'MY_TOPIC', payload: {} }
  }
}

After

{
 // ...
  resolve: (events) => {
    console.log(events) // [{ topic: 'MY_TOPIC', payload: {} }]
  }
}