[Feature] Add subgroups to organise inside groups (Telegram "subjects")

[wyllyjon]

Is there an existing request for feature?

• I have searched the existing issues

What feature would you like?

I would like the possibility to add subgroups to groups, like Telegram do.
It allow users to have less groups, and allow to organize better data in groups.

Anything else?

No response

[KeeJef]

Similar to #629 and oxen-io/session-desktop#2041

[LuLuLoLu]

Tracked internally in SES-427

[wyllyjon]

Didn't meant like #629, not categorising groups by categories (displayed as tabs in telegram), but having subgroups inside the groups, what Telegram call "subjects".
Sorry, my initial message wasn't clear.