[BUG][BACKWARDS_COMPATIBILITY] Updates from URI-in-databag broken

[juditnovak]

See: https://github.com/canonical/pgbouncer-operator/actions/runs/8639099075/job/23697059499#step:21:456

The deeper issue (or an additional consequence?) was that the secret from internal label (URI) got the first secret group assigned as label.

ubuntu@vm-lxd:~$ juju show-secret --reveal coc30v0ap9rj9bc4n6a0
coc30v0ap9rj9bc4n6a0:
  revision: 4
  owner: pgbouncer
  label: pgbouncer.app.user
  created: 2024-04-11T18:48:29Z
  updated: 2024-04-11T21:17:41Z
  content:
    auth-file: |-
      "pgbouncer_auth_relation_6" "md5e56f74ca75a73e9746b891a61f9fd888"
      "pgbouncer_stats_pgbouncer" "md59c1005d6dde73f766e6b03bac3294efc"
    cfg-file: "[databases]\npostgresql_test_app_first_database = host=10.99.134.44
      dbname=postgresql_test_app_first_database port=5432 auth_user=pgbouncer_auth_relation_6\n\n[pgbouncer]\nlisten_addr
      = 127.0.0.1\nlisten_port = 6432\nlogfile = /var/lib/postgresql/pgbouncer/pgbouncer.log\npidfile
      = /var/lib/postgresql/pgbouncer/pgbouncer.pid\nadmin_users = \nstats_users =
      pgbouncer_stats_pgbouncer\nauth_type = md5\nuser = snap_daemon\nmax_client_conn
      = 10000\nignore_startup_parameters = extra_float_digits,options\nserver_tls_sslmode
      = prefer\nso_reuseport = 1\nunix_socket_dir = /var/lib/postgresql/pgbouncer\npool_mode
      = session\nmax_db_connections = 100\ndefault_pool_size = 5\nmin_pool_size =
      3\nreserve_pool_size = 3\nauth_query = SELECT username, password FROM pgbouncer_auth_relation_6.get_auth($1)\nauth_file
      = /var/snap/charmed-postgresql/current/etc/pgbouncer/pgbouncer/userlist.txt\n\n"
    monitoring-password: rVhoyYk3uGU0xbgHy4XISneV
    relation-id-7: xSoOaBtBmvXJ870bSYTGB2ZR

For more context a more detailed explanation of the problem here: https://github.com/canonical/data-platform-libs/pull/157#issuecomment-2061980265

[github-actions[bot]]

https://warthogs.atlassian.net/browse/DPE-4054