Meeting.create: make duplicate from (optionally) mandatory

[Elblinator]

Context: The new setting from the Meta-Issue OpenSlides/openslides-meta#125

For committeeadmins: If this setting is active then only templates should be returned as potential candidates to duplicate a meeting from
For Orgaadmins and superadmins: The displayed list should be the same as before

[ostcar]

I need more context for this. Which field from the models.yml has to change for this?

I would have guessed, that nothing has to change in the autoupdate service, but the client shows, which meetings can be used for cloning and the backend enforces this

[rrenkert]

Maybe there is nothing to do here, we have to check which subscriptions come from the client for the 'duplicate from' field.
I will ping or close here after clarification.

[Elblinator]

The feature indeed didn't need any changes from the autoupdate :)