New “Ephemeral conversation” mode needed

[!TIP]

How to use GitHub

• Please use the 👍 reaction to show that you are affected by the same issue.
• Please don't comment if you have no relevant information to add. It's just extra noise for everyone subscribed to this issue.
• Subscribe to receive notifications on status change and new comments.

Here’s a problem that, in my humble opinion, is limiting in day-to-day work with Nextcloud Talk.

At work (Arawa), I have a dedicated meeting room (called i.e. “Jérôme's conversation”) that I use 99% of the time for video conferencing. I use it to talk with one or more colleagues and/or a client. The problem is that participants remain on the participant list even after the call has ended.

For confidentiality reasons, especially regarding clients, I have to manually remove all previous participants every time.

If I ever forget to do this preliminary cleanup of participants (which is tedious):

• all previous participants are notified of any new call (unless, by chance, I decided to start the call silently)
• all new participants know who was in the room during the previous call

The problem is that Talk conversations are a hybrid of instant messaging and video conferencing.

I therefore suggest that you add a new “Ephemeral conversation” mode. This setting could be configured on a per-room basis and would ensure that participants are never saved.

Characteristics :

• A participant would ONLY appear if they joined the conversation (regardless of whether it’s for instant messaging or video conferencing). They would IMMEDIATELY disappear from the participant list as soon as they leave the room (whether by switching rooms or closing the tab).
• This mode would also automatically and IMMEDIATELY delete all written messages (chat history), attachments, and so on as soon as EVERYONE (including the organizer) has left the conversation.

Feature request

Which Nextcloud Version are you currently using: (see administration page)
Is your feature request related to a problem? Please describe.
Provide a clear and concise description of the problem. For example: “I'm always frustrated when …”

Describe the solution you'd like
Provide a clear and concise description of what you want to happen.

Describe alternatives you've considered
Provide a clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots related to the feature request here.

Start by mapping how Talk currently handles participant lists, chat history, and room join/leave events. Compare the requested per-room behavior with existing conversation and call lifecycle semantics; done means participants are only visible while present and conversation content is removed after everyone leaves.