load mongo object while transporting to ES

[mzahidriaz]

{
  objectId: 12312312312312312,
  name: "Some name",
  anotherDocId: 12312312323123123123
}

While transporting this to ES I want to load anotherDocId from mongo and add as a json object before transporting to ES.

Expected Output

{
  objectId: 12312312312312312,
  name: "Some name",
  anotherDocId: {
    name: "Another Document Name"
  }
}

[jipperinbham]

this would be implemented as part of #39