FIX: show too long message error on client (#27794)

Prior to this fix we would show the message after a round trip to the server. If you had a too long message error, at this point your input would be empty and we would show an error in chat. It's important to have this server side safety net, but we can have a better UX by showing an error on the frontend before sending the message, that way you can correct your message before sending it and not lose it.

plugins/chat/spec/system/page_objects/chat/chat_channel.rb

@@ -35,7 +35,9 @@ module PageObjects
       end
 
       def click_composer
-        find(".chat-channel .chat-composer__input").click # ensures autocomplete is closed and not masking anything
+        if has_no_css?(".dialog-overlay", wait: 0) # we can't click composer if a dialog is open, in case of error for exampel
+          find(".chat-channel .chat-composer__input").click # ensures autocomplete is closed and not masking anything
+        end
       end
 
       def click_send_message

plugins/chat/spec/system/page_objects/chat/chat_thread.rb

@@ -94,7 +94,9 @@ module PageObjects
       end
 
       def click_composer
-        find(".chat-thread .chat-composer__input").click # ensures autocomplete is closed and not masking anything
+        if has_no_css?(".dialog-overlay", wait: 0) # we can't click composer if a dialog is open, in case of error for exampel
+          find(".chat-thread .chat-composer__input").click # ensures autocomplete is closed and not masking anything
+        end
       end
 
       def send_message(text = nil)

plugins/chat/spec/system/page_objects/chat/components/composer.rb

@@ -48,6 +48,10 @@ module PageObjects
           input.value
         end
 
+        def has_value?(expected)
+          value == expected
+        end
+
         def reply_to_last_message_shortcut
           input.click
           input.send_keys(%i[shift arrow_up])