WABP: Support incoming text message in webhook

[nbartels]

Receiving a incoming whatapp text message can trigger the webhook. Our mapper needs to be able to map the incoming json to a good object structure.

Example json:

{
  "object": "whatsapp_business_account",
  "entry": [
    {
      "id": "101809759215303",
      "changes": [
        {
          "value": {
            "messaging_product": "whatsapp",
            "metadata": {
              "display_phone_number": "1234567891",
              "phone_number_id": "10634295353625"
            },
            "contacts": [
              {
                "profile": {
                  "name": "TestUser"
                },
                "wa_id": "491234567890"
              }
            ],
            "messages": [
              {
                "from": "491234567890",
                "id": "wamid.HBgNNDkxNTIwOTgzMzM5OBUCABIYHGDEHJVFHJEVCFHJEVBCMTkyODk1OEIyAA==",
                "timestamp": "1653253313",
                "text": {
                  "body": "Test"
                },
                "type": "text"
              }
            ]
          },
          "field": "messages"
        }
      ]
    }
  ]
}