Adding debugging for webhook (#7199)

* Adding debugging for webhook

* Fixing build error

* Moving error down

api4/webhook.go

@@ -476,7 +476,12 @@ func incomingWebhook(c *Context, w http.ResponseWriter, r *http.Request) {
 		}
 	}
 
-	parsedRequest := model.IncomingWebhookRequestFromJson(payload)
+	parsedRequest, decodeError := model.IncomingWebhookRequestFromJson(payload)
+
+	if decodeError != nil {
+		c.Err = decodeError
+		return
+	}
 
 	err := app.HandleIncomingWebhook(id, parsedRequest)
 	if err != nil {