Add a way for cooks to edit mensas they are cooking for

[SubSide]

As a cook I want to be able to change certain parts to the mensa I'm cooking for.

Acc 1: Cooks should only be able to edit mensas they are signed up as cooks for (they should only be able to be signed up as cooks by an admin)
Acc 2: Cooks should only be able to edit certain fields: Title, description, menu. All other options are only editable by an admin.