Checkmk Werk 13380: Validate use of contact groups in dashboards on deletion

ID: 13380 Title: Validate use of contact groups in dashboards on deletion Component: Setup Level: 1 Class: Bug fix Version: 2.1.0i1 If a contact group was removed that was still used in a dashboard, the contact group was silently removed from the dashboard and it may no longer be possible to access the dashboard.