Allow Users to authenticate if room has guests allowed/enabled

[LexioJ]

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Feature request

Which Nextcloud Version are you currently using: 29.0.8

Is your feature request related to a problem? Please describe.
When joining a meeting where guests are allowed but without establishing a session in the browser beforehand, users with accounts are joined as guests.

Describe the solution you'd like
Add an option to logon and join instead of using a guest account for "full-access"-users

Describe alternatives you've considered
none

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

[Antreesy]

Added in Nextcloud 30.0.0 / Talk 20.0.0