Need advice on extension to rt command line

I’d like to manipulate users from the rt command line,
specifically to show the groups the user belongs to,
and to add or delete the user from a given group.
(I’m working on RT 3.4.2, but it seems 3.4.5 is the same.)

I think (guess) the syntax ought to be:

rt show user/22/groups

rt edit user/22 add groups=mygroup,yourgroup

rt edit user/22 del groups=someothergroup

rt edit user/22 set groups=hisgroup,hergroup

Also, I’m a little unclear where the code would go.
I think my choices are:

…/share/html/REST/1.0/Forms/user/default (which exists)
…/share/html/REST/1.0/Forms/user/groups (which doesn’t exist yet)

It seems the edit command would go in Forms/user/default,
but the show could go either in default or in a new file, groups.

Is there a clear “RT way” to do this?