Communication: Support for Course-wide Group Chats

[JanaNF]

Is your feature request related to a problem?

Currently, there is no straightforward way to create course-wide group chats. The only new created course-wide channels are (automatically) lectures, exams and exercises. For instance, in ITP, we manually created course-wide channels after the fact and had to add all participants individually.

Describe the solution you'd like

• Add an option to create course-wide group chats directly during the chat creation process. This option would appear alongside "Public" and "Private" as a new type, e.g., "Course-wide." Or as a checkbox "Do you want to make it course wide" after selecting "Public"/"Private".
• Server-side changes should be minimal, as the logic likely mirrors existing group chat structures with broader participant scope.
• On iOS (or other platforms), implementing the client-side logic would be straightforward once the server supports this functionality.

Describe alternatives you've considered

No response

Additional context

Avoid post-hoc conversions: Retroactively converting existing channels to course-wide is not recommended, as it may introduce complications and is slow. Instead, focus on providing a clear and easy setup during chat creation.