Forum OpenACS Q&A: Subclassing parties/users/people (or user-specific data)

Greetings,

In ACS 3.4.x you could designate that a member of a group had some
specific data associated with his membership.  That ability seems to
have disappeared in the 4.x series.  Can anyone comment on the best
way to do this?  For example, if a user is a member of a particular
group we need to keep some extra data about him--like an internal
customer number or a region code.  This data varies depending on the
type of user that he is.

I've considered subclassing the user, person, or parties type so I
could use object attributes, but that seems like it would take a lot
of work because the 'add user' pages would have to be re-worked to
add the data.  Then I also have the problem of what happens if a user
becomes a different type of user.

I'm trying to do this so I won't wreak havoc when new versions of the
toolkit come out.

Any suggestions appreciated.