code: async def message(**payload):
      
      data = payload["data"]
      web_client = payload["web_client"]
      channel_id = data.get("channel")
      user_id = data.get("user")
      text = data.get("text")
  
      if text and text.lower() == "start":
          return await start_onboarding(web_client, user_id, channel_id)
docs: Display the onboarding welcome message after receiving a message
      that contains "start".