Successfully reproduced the bug in camunda BPM 7.1.1 and 7.1.2
A usergroup with slashes in the group ID can be created without any errors. Application access, Authorizations and Group Member Authorizations can be set and deleted without any errors.
When adding a user to the usergroup, the following error message appears: Communication Error: The application received an unexpected 400 response from the server. Try to refresh the page or login and out of the application.
This only occurs on the 7.1 branch and not on the 7.2 branch and seems to be an encoding issue with the REST API.
When hitting the group ID or the "edit" button in the group tab, the page redirects to the user tab. Therefore, the usergroup can not be modified or deleted. This occurs on the 7.1 and on the 7.2 branch.
I can not edit, delete or add users to groups with a slash in the group ID
Access to the edit screen and ability to add users to the group