Make Kafka Output a first class typed citizen

[marcelmedina]

It hurts my eyes to see the escaped JSON assigned to string kevent:

[Function("KafkaOutputWithHeaders")]

public static MultipleOutputType Output(
    [HttpTrigger(AuthorizationLevel.Anonymous, "get", Route = null)] HttpRequestData req,
    FunctionContext executionContext)
{
    var log = executionContext.GetLogger("HttpFunction");
    log.LogInformation("C# HTTP trigger function processed a request.");

    string message = req.FunctionContext
                        .BindingContext
                        .BindingData["message"]
                        .ToString();
    string kevent = "{ \"Offset\":364,\"Partition\":0,\"Topic\":\"kafkaeventhubtest1\",\"Timestamp\":\"2022-04-09T03:20:06.591Z\", \"Value\": \"" + message + "\", \"Headers\": [{ \"Key\": \"test\", \"Value\": \"dotnet-isolated\" }] }";
    var response = req.CreateResponse(HttpStatusCode.OK);
    return new MultipleOutputType()
    {
        Kevent = kevent,
        HttpResponse = response
    };
}

Please make it strongly typed. This implementation needs improvement.