The hive collector's `oauth2client` secret came from a `clientSecretFile`
defaulting to authelia's own minted file on the IdP's host, with a
`hive-otel-client-secret` oneshot that only waited up to 120s for that
file to exist; any other hive had to copy the file across by hand.
`swarm-bao-hive-otel-oidc` now logs in with the hive's leaf
(`deploy.bao.clientCertFile`), reads `swarm/hives/<hive>/oidc/client`
(written by the publisher, granted by the hive leaf's
`swarm/hives/<hive>/*` read), writes it root 0400 when it differs, and
restarts the collector when the file is newer than its last start.
Retries every 30s for 24h (`lib/store-retry.nix`), like the matrix and
forge fetches. `clientSecretFile` defaults to that file wherever the hive
leaf is set and stays as an override; an overridden file renders no fetch.
otelcol-contrib 0.151.0's oauth2client re-reads `client_secret_file` on
every token fetch, but the path is `LoadCredential`'s start-time copy, so a
changed secret still needs a restart. `lib/refresh-consumer.nix` gains
`refresh_unit` for a host unit; `refresh_consumer` now calls it with
`--machine`.
nats-authelia's "consumer of the host client-secret dir" case pointed at
the collector's old default; it now reads the publisher's path unit.
Refs #5015
7c50568db1