CMS -> control panel -> permissions, does not properly merge authroles

The repository merges different hipposys:authroles nodes for the same role, but the CMS interface does not.

Reproduction path:
create two groups, group1 & group2
give group1 a role on a domain (ex. role readonly on domain everywhere)

go to the console
navigate to the domain
copy the hipposys:authrole
change the group on the lowest (order) node to group2

Go back to the CMS, look at the permissions screen

Expected:
Both groups have the permissions associated with the role, and both groups are shown having the role

Actual:
Both groups have the permissions associated with the role, but only group2 is shown having the role

Consequences:
It's now impossible to revoke the rights of group1, adding the group to the role only modifies the second authrole node, original one stays intact.