Treat parent-group membership as effective membership

## What

treat/display effective parent-group membership (user belongs to parent groups of their subgroups; LDAP provider should expose those parents in memberOf).

## Want

- Treat/display effective parent-group membership (user belongs to parent groups of their subgroups
- LDAP provider should expose those parents in memberOf)

## Ideas this came from

- [#9246 Feature Request: Display all parent groups for user groups](https://github.com/goauthentik/authentik/issues/9246) — We have a lot of groups with nested groups, in some services we use many combinations of groups. And we want to see all groups with parent groups, because it lo
- [#14821 option for implicit membership of parent group for members of subgroup](https://github.com/goauthentik/authentik/issues/14821) — I am currently working for an organization, in which roles are redistributed every year. We are using groups to mirror those roles, which are used by different
- [#21950 LDAP Provider: expose effective parent groups for users](https://github.com/goauthentik/authentik/issues/21950) — Is your feature request related to a problem? Please add an optional LDAP Provider setting to expose effective group membership for users, including parent grou

Start by locating the group-membership implementation and the LDAP provider entry point. Trace how subgroup membership is currently calculated and exposed through memberOf, then determine the expected behavior for nested parent groups and how it should be displayed. Done means effective parent membership is consistently represented in both areas, with tests covering nested groups.

Written by the indexing model from the issue text.