Add a listener to make it possible to return updated data from add/edit actions

[AD7six]

The response from an edit action is for example:

{
  "success": true,
  "data": {}
}

An optional listener such that the data is populated with the updated data would be useful in some cases.

For example, where the input data is sanitiazed/prepared, or completely transformed (file uploads) and the client would need to know what the updated/saved data looks like. The client could of course immediately request the view of the same resource, but that's one extra api roundtrip.