Need to include properties with body

[WilliamBradee]

Azure event hub allows sending properties along with the body.

See JavaScript example at https://learn.microsoft.com/en-us/azure/event-hubs/add-custom-data-event

this is the essence from that link:

let eventData = { body: "First event", properties: { "event-type": "com.microsoft.samples.hello-event", "priority": 1, "score": 9.0 } };

Allow msg.properties and if they are there, add them when the message is built.

I tested this in line 101 of index.js

const isAdded = batch.tryAdd(msg.properties === undefined ? { body: msgJSON } : {body: msgJSON, properties : msg.properties});