using a better method to retrieve start message for thread (Together-…

…Java#1106)

* using a better method to retrieve start message for thread

* replace retrieveMessageById with getStartMessage on threadChannel channel type

application/src/main/java/org/togetherjava/tjbot/features/help/HelpThreadCreatedListener.java

@@ -97,8 +97,7 @@ private static boolean isPostedBySelfUser(Message message) {
     }
 
     private RestAction<Message> createAIResponse(ThreadChannel threadChannel) {
-        RestAction<Message> originalQuestion =
-                threadChannel.retrieveMessageById(threadChannel.getIdLong());
+        RestAction<Message> originalQuestion = threadChannel.retrieveStartMessage();
         return originalQuestion.flatMap(HelpThreadCreatedListener::isContextSufficient,
                 message -> helper.constructChatGptAttempt(threadChannel, getMessageContent(message),
                         componentIdInteractor));
@@ -110,7 +109,7 @@ private static boolean isContextSufficient(Message message) {
     }
 
     private RestAction<Void> pinOriginalQuestion(ThreadChannel threadChannel) {
-        return threadChannel.retrieveMessageById(threadChannel.getIdLong()).flatMap(Message::pin);
+        return threadChannel.retrieveStartMessage().flatMap(Message::pin);
     }
 
     private RestAction<Message> generateAutomatedResponse(ThreadChannel threadChannel) {
@@ -172,7 +171,7 @@ public void onButtonClick(ButtonInteractionEvent event, List<String> args) {
         ThreadChannel channel = event.getChannel().asThreadChannel();
         Member interactionUser = Objects.requireNonNull(event.getMember());
 
-        channel.retrieveMessageById(channel.getId())
+        channel.retrieveStartMessage()
             .queue(forumPostMessage -> handleDismiss(interactionUser, channel, forumPostMessage,
                     event, args));