Change GroupRelationship id for compatibility with subgroup module

Problem/Motivation

The subgroup and ggroup modules have different advantages. Is it possible to use both of them in the same installation?

I created a test site with both enabled, and it seemed like the only thing I could use in the UI was the subgroup module. When I uninstalled that, then the ggroup UI became available.

Trying to add subgroup to a site where I had previously used ggroup failed with fatal errors about a missing plugin, but I wasn't sure if that was related to having already created group types and groups without having had the module installed.