FIX: webhook should touch channel’s last_message_sent_at (#19342)

plugins/chat/app/controllers/chat_controller.rb

@@ -110,7 +110,6 @@ class Chat::ChatController < Chat::ChatBaseController
 
     return render_json_error(chat_message_creator.error) if chat_message_creator.failed?
 
-    @chat_channel.touch(:last_message_sent_at)
     @user_chat_channel_membership.update(last_read_message_id: chat_message_creator.chat_message.id)
 
     if @chat_channel.direct_message_channel?

plugins/chat/lib/chat_message_creator.rb

@@ -53,6 +53,7 @@ class Chat::ChatMessageCreator
         chat_message: @chat_message,
         timestamp: @chat_message.created_at,
       )
+      @chat_channel.touch(:last_message_sent_at)
       DiscourseEvent.trigger(:chat_message_created, @chat_message, @chat_channel, @user)
     rescue => error
       @error = error

plugins/chat/spec/components/chat_message_creator_spec.rb

@@ -112,6 +112,18 @@ describe Chat::ChatMessageCreator do
       }.to change { ChatMessage.count }.by(1)
     end
 
+    it "updates the channel’s last message date" do
+      previous_last_message_sent_at = public_chat_channel.last_message_sent_at
+
+      Chat::ChatMessageCreator.create(
+        chat_channel: public_chat_channel,
+        user: user1,
+        content: "this is a message",
+      )
+
+      expect(previous_last_message_sent_at).to be < public_chat_channel.reload.last_message_sent_at
+    end
+
     it "sets the last_editor_id to the user who created the message" do
       message =
         Chat::ChatMessageCreator.create(