- controller golem15.user.usergroups behind golem15.users.access_groups
- list with users_count from the list's own query; form with the checkbox
permission editor stored in user_groups.permissions
- creating a group with a privileged code, changing a code to or from one and
deleting a privileged group need golem15.users.manage_privileged_groups
- a group delete removes its users_groups rows in the same transaction
- UserGroup gains Fillable, Rules and the read-only UsersCount; PermissionSet.Text
- TestAdminGroups and the D-06 matrix in TestAdminPrivilegedGroups
- user_groups (seeded with the guest and registered groups) and the
users_groups pivot, folded from the PHP v1.1.1 and v2.8.0 migrations
into migration 202610020001_create_user_groups
- models.UserGroup and a User.Groups relation that is never serialized
- classes.UserGroupCodes and classes.HasGroupCode for server-side checks
such as the site-admin group code admin
- additive only: no route, payload or existing column changes; the user
payload still answers "groups":[]
