Guests can start new conversations ad libitum

I realized that despite having only a limited guest account, users can start any desired conversation (such as public ones, or one-to-one conversations with any user on the server) via the Android Talk app (13.0.0 RC1 via GPlay Beta)

Steps to reproduce

1. Log into server with a guest account
2. Click on "+" to start new conversation, select what you would like to do
3. Create conversations ad libitum

Expected behaviour

Guest accounts should have the same restrictions in the Android app as in the server app - but judging from the possibility to create any conversation desired, this is also linked to the Talk server API that doesn't prevent this?

Actual behaviour

Guests can start any conversation the want, including one-to-one with full search capabilities among all server users.

Device information

Device: Google Pixel 4
Android version: 12

Talk version: 13.0.0

Server information

Nextcloud version: 23 RC

Talk version: 13

Start by reproducing the guest-account flow in the Android Talk app and inspect the conversation-creation path and the Talk server API involved. Compare guest permissions with the server app's restrictions; done means guests cannot create unrestricted conversations or search and message arbitrary users.