Clojure wrapper for the Google Admin SDK Directory API.

Provides idiomatic Clojure functions for managing users, groups,
group members, and organizational units in a Google Workspace domain.

Auth: use csl/scoped-delegated-credentials with the appropriate scope
and a super-admin impersonation target:
- DirectoryScopes/ADMIN_DIRECTORY_USER                       (user read/write)
- DirectoryScopes/ADMIN_DIRECTORY_USER_READONLY
- DirectoryScopes/ADMIN_DIRECTORY_GROUP                      (group read/write)
- DirectoryScopes/ADMIN_DIRECTORY_GROUP_READONLY
- DirectoryScopes/ADMIN_DIRECTORY_GROUP_MEMBER               (member read/write)
- DirectoryScopes/ADMIN_DIRECTORY_GROUP_MEMBER_READONLY
- DirectoryScopes/ADMIN_DIRECTORY_ORGUNIT                    (org unit read/write)
- DirectoryScopes/ADMIN_DIRECTORY_ORGUNIT_READONLY
- DirectoryScopes/ADMIN_DIRECTORY_ROLEMANAGEMENT_READONLY    (roles + assignments read)
- DirectoryScopes/ADMIN_DIRECTORY_USER_SECURITY              (tokens/mobile/ASPs — read + revoke;
                                                              this library only exposes reads)
- DirectoryScopes/ADMIN_DIRECTORY_DOMAIN_READONLY            (domains read)
- DirectoryScopes/ADMIN_DIRECTORY_RESOURCE_CALENDAR_READONLY (calendar resources read)

All list functions return {:data [...] :next-page-token "..."}.
:next-page-token is absent when there are no further pages.

Update semantics: functions named update-* use PATCH (partial update);
functions named replace-* use PUT (full replacement). Both return
the updated resource.

All functions return {:data ...} on success or {:error ...} on failure.