The tmpfiles `r` rule for the stale `oidc-client.secret` in the
swarm-nats container sat in swarm-nats.nix under `deploy.nats.enable`,
so a host that turned the queue off kept the copy. It now sits in the
ungated removal shim next to the seed copies' rules, which is where the
S2 plan put it and the one file to delete when the deprecation window
closes. The module-eval case asserts the rule on a host with the queue
off as well.
`swarm-bao-nats-callout-xkey` runs `ensure-callout-keys`, importing
/var/lib/swarm-nats-callout/{issuer,callout-user}.seed when present so the
keys keep their public halves, then fetches all three public halves from
the store. The verb removes each seed file once a read of the store returns
a seed; when the store's seed differs, it is kept and a warning names the
file. No tmpfiles rule touches those files, since one could run before the
import with the store sealed and leave the next run to mint a new key.
The server renders the issuer and user public halves from the fetched files,
checked for shape as the xkey's is, and does not start without them. The
responder reads both seeds from the store, so the copies into the container
and their LoadCredential entries are gone, and a tmpfiles rule removes the
copies a container still holds. `swarm-nats-callout-keys` is removed.
On the store's host the fetch unit is also ordered after
`swarm-bao-secret-publisher-policy`, so the publisher's denial of the seed
paths is written before the unit creates or keeps a seed there.
`deploy.nats.autoGenerateCallout`, `calloutUserPublicKey`,
`calloutIssuerPublicKey`, `calloutUserSeedFile` and `calloutIssuerSeedFile`
are removed with `mkRemovedOptionModule`, under `swarm.nats` too, each
message saying the keys live in the store.
