WABP: incoming sticker message

[nbartels]

{
  "object": "whatsapp_business_account",
  "entry": [
    {
      "id": "101809759215303",
      "changes": [
        {
          "value": {
            "messaging_product": "whatsapp",
            "metadata": {
              "display_phone_number": "123456789",
              "phone_number_id": "1063423435420583"
            },
            "contacts": [
              {
                "profile": {
                  "name": "TestUser"
                },
                "wa_id": "491234567890"
              }
            ],
            "messages": [
              {
                "from": "491234567890",
                "id": "wamid.HBgNNDkxNTIwOTgzMzMGDHEVFEJHFCIYFDNBMUNCMzAwRTQ5RDBDRUE4NzJDAA==",
                "timestamp": "1653318440",
                "type": "sticker",
                "sticker": {
                  "mime_type": "image\\/webp",
                  "sha256": "RZEEl5HVWT4S6C0PoOgjYCQVDWs5esIMJsjcDYI80ZE=",
                  "id": "1122990445227715"
                }
              }
            ]
          },
          "field": "messages"
        }
      ]
    }
  ]
}