Modify existing chat + RAG cookbook to include previous user chat messages

[mrm1001]

Modify the demo colab to support memory for user messages.

[TuanaCelik]

For context: deepset-ai/haystack-cookbook#90

This is the PR that we were about to merge in the cookbooks repo. But we didn't because of the user messages not being saved in memory.

[julian-risch]

@vblagoje Let's talk about this issue when you start working on it.

[vblagoje]

For increased visibility: @annthurium @TuanaCelik I have updated the proposed notebook to include user's questions. The main change is the direct question injection into OutputAdapter which in turn saves both question and answer (we already saved that one). I adjusted prompt a bit and used gpt-4 to get fewer "wrong" answers.

I suggest to devrel team to take the notebook referenced above, run it yourself, adjust it where needed (perhaps reduce verbosity etc) and LMK if there is anything else needed for it.

[TuanaCelik]

@vblagoje - thanks for creating this. However this leaves me with the question about the output adaptor. I thought there was some work by you and @julian-risch to remove the output adaptor? In this scenario we need to have it in here because it's the only way we have the user messages correct?

[TuanaCelik]

May I suggest a solution similar to this: https://colab.research.google.com/drive/1kJqMWRrP96YoXek6WIZNlnh-fW1fRvKe?usp=sharing

This means users do not have to worry about output adapters etc as it's all wrapped up in a Memory component.
AND, since Vlad is working on a message writer, we may also not even need that!