Groups owning metadata can be deleted

[josegar74]

Tested in 3.8.x

1. Create some records and assign to the default Sample group

2. Edit the Sample group and delete it --> No error is displayed, the group is removed

3. Go to the editor dahsboard --> The metadata group owner has the id (2) of Sample group, but as the group no longer exists the id is displayed instead of the group name.

Probably no FK between metadata and groups, but this should be prevented. If the group has metadata should not be possible to be deleted.

In these cases, the metadata should be transfer to other group first and the can be deleted.

Also to consider if the group has users assigned, maybe to warn the user before deleting the group. For now just get unlinked.