fix(cabana): bulk lifecycle actions change every selected administrator

actionDB returned the Unscoped instance of the action's session, whose
conditions accumulate, so a bulk activate, deactivate or restore of two
applicable rows wrote only the first (the second update matched
"id = A AND id = B") while still counting it. A bulk deactivate
therefore left the other administrators active and signed in (D-10,
D-12). actionDB now ends with a plain Session, so every query starts
anew. Found by TestAdministratorsLifecycle.

modules/cabana/backend_users_admin.go

@@ -296,13 +296,16 @@ func (c usersAdmin) lifecycles() []usersLifecycle {
 	}
 }
 
-// actionDB is the action's write transaction as a fresh, unscoped session.
+// actionDB is the action's write transaction as a fresh, unscoped session
+// that every query starts from anew. The final Session matters: Unscoped
+// returns an instance whose conditions accumulate, so a bulk action's
+// second "id = ?" update would otherwise match no row.
 func actionDB(ctx context.Context) (*gorm.DB, error) {
 	tx, ok := TxFromContext(ctx)
 	if !ok {
 		return nil, errors.New("cabana: administrators: an action needs its transaction")
 	}
-	return tx.Session(&gorm.Session{NewDB: true}).WithContext(ctx).Unscoped(), nil
+	return tx.Session(&gorm.Session{NewDB: true}).WithContext(ctx).Unscoped().Session(&gorm.Session{}), nil
 }
 
 // AdminRecordActions are Activate, Deactivate and Restore on the preview