Fix user linking

backend/src/main/resources/db/migration/V9__backfill_user_accounts.sql

@@ -41,11 +41,13 @@ WHERE e.user_id IS NULL
 
 UPDATE customer c
 JOIN users u ON u.email = c.email
+   AND u.role = 'CUSTOMER'
 SET c.user_id = u.id
 WHERE c.user_id IS NULL;
 
 UPDATE employee e
 JOIN users u ON u.email = e.email
+   AND u.role IN ('STAFF', 'ADMIN')
 SET e.user_id = u.id
 WHERE e.user_id IS NULL;