Don't render deleted messages

[andrii-i]

Problem

Currently when messages is deleted it is still rendered in UI as (message deleted). It seems to not bring any useful information and increase visual clutter.

Proposed solution

Do not render deleted messages.

Before this PR:

After this PR:

[github-actions]

👈 Launch a Binder on branch andrii-i/jupyter-chat/no_show_deleted_msgs

[ellisonbg]

Nice! Could you create another screenshot to show the view before the messages are deleted?

[andrii-i]

@ellisonbg it was already present in "Problem" section unless I misunderstand. I moved it to the "Proposed solution" section and added "Before this PR:" note just before the screenshot for more visibility.

[ellisonbg]

Clarification: I was hoping you could show the messages before the user hit the delete button to delete the messages in the first place. Looking for before and after the user hits delete, rather than only before and after the PR.

[andrii-i]

@ellisonbg thank you for the clarification, updated screenshots based on it.

[brichet]

Thanks @andrii-i for working on this.

I think this is a matter of opinion, and agree that in the context of a conversation with an AI it doesn't make sense to keep this track.
In a regular use of the chat, I always find it frustrating when I saw an information and cannot retrieve any track of it in the history (like in Slack I think). In most of the others chat that I know, the message deleted is kept (gitter, zulip, whatsapp...).

Since this PR doesn't actually remove the message from the shared document (only avoid displaying it), I would add a user setting for it.

[andrii-i]

Thank you for looking into this @brichet. I agree that this is a matter of opinion, that both approaches have tradeoffs, and indeed believe that approach presented in this PR in the context of a conversation with an AI makes sense.

In a regular use of the chat, I always find it frustrating when I saw an information and cannot retrieve any track of it in the history (like in Slack I think). In most of the others chat that I know, the message deleted is kept (gitter, zulip, whatsapp...).

Since this PR doesn't actually remove the message from the shared document (only avoid displaying it), I would add a user setting for it.

Would you be open to merging this PR and then following up with another PR later on the settings? Another way to deal with being able to retrieve messages could be be wiring up undo/redo so users can undo deleted messages to recover them.

[andrii-i]

@brichet I've created #237 as a placeholder for task on rendering deleted messages setting

[brichet]

@andrii-i what I meant was not being able to retrieve the message (currently the content is deleted anyway and I think it's fine), but rather being able to know that message has been deleted. The current behavior looks fine for me.
The settings I mentioned could be only a boolean, whether to display or not the deleted messages, to let users choose the behavior.