Add an attribute to get all the conversation messages

Add the attribute "conversationMessages" that contains all the messages exchanged during the conversation. It is very useful to create messaging contexts used in chatGPT Prompt creation. Example: GPT Prompt: From the user contexct below try to understand how much is he happy about the conversation and reply with a number from 1 to 10, where 1 is unhappy and 10 is really happy. User context: {{conversationMessages}}