Meeting creation: permission problem

[MSoeb]

Description: When creating new meetings, it is possible for all committee admins to access the entire pool of ALL active meetings and use them as a basis for a new meeting. This is incorrect behavior, as it allows access to meeting for which a committee admin previously had no access.

Example image - committee admin have access to all active meetings

Reproduction:

1. create two committees (A and B)
2. create in both committees a meeting which is active
3. create a new user XYZ and add to committee A as committee admin
4. Log in as user XYZ and open committee A
5. create a new meeting. in the template field the meeting from committee B should be visible

What should happen?
When creating new meetings by duplication, it should only be possible to use meeting templates or meetings of the committee in which the new meeting should be created. Meetings for which the committee admin does not have access authorization, i.e. which are not part of the committee or a template, should not be displayed in the list of possible meetings for duplication.