WeblatePermission: Handle user renames correctly.

Create a userdb_cache that ships a username -> id link to check renames.

fixes: https://gitlab.torproject.org/tpo/tpa/tails/sysadmin/-/issues/18144

files/config/weblate_permissions.yaml

@@ -361,3 +361,4 @@ superusers:
 - drebs
 - hefee
 - intrigeri
+userdb_cache: /var/lib/weblate/userdb_cache.yml