Currently, list=allusers supports querying for users by their user_group using the augroup parameter. This is great and very useful. I'd also like to query users by their user_former_group. So I propose that we add a parameter called something like "auformergroup" that would allow for joining this table with user too.
Given that user_former_group seems to have similar indexes, I don't think this will incur any concerning additional load on the DBs.
query=userinfo and query=users should have a formergroups too