Admin: warning to user, when change affects lots of data entries

[neoheat]

🚀 Feature Request

Is your feature request related to a problem? Please describe.

When a role is customized for users of an inventory park, inexperienced users may unconsciously adjust the rights of an entire group instead of just those of individual users.

Describe the solution you'd like

The user should be warned, if such a role change affects a lot of users. To execute the action, the administrator who performs this change, should be prompted with a warning. The number of data entries to be changed should be displayed in the warning message.

[neoheat]

this message should also appear in the "global" group https://test.leihs.zhdk.ch/admin/groups/4dd87663-f731-5766-b97d-9494889ca66c