Authelia reads authentication_backend.file.path once at startup. Without
watch, an identity the bridge creates is real on disk and invisible to the
running authelia until something unrelated bounces the unit.
swarm-authelia-bridge cannot restart authelia -- running unprivileged
inside the container is the whole reason it may write that file, so
restarting the unit is exactly the privilege it was designed not to hold.
swarmctl does restart it, but that is a systemctl -M shellout that can
fail, and when it did the symptom was a login refused for a user whose
record was already correct on disk. This makes correctness stop depending
on that restart succeeding.