JSON payload issues with Azure Functions

[khilscher]

I saw several students who had malformed JSON payloads. E.g. missing device ID, using "temp" instead of "Temperature", etc. I think we need to make it very clear in the documentation that the payload must match the sample_payload.json 100% or else the Function will likely fail. Suggest we also add a try/catch block inside the Function to validate the payload before processing and display a "Invalid Json payload" message if validation fails. If you want me to do this, just assign this issue to me.