Those names are certified by the swarm-services sub-CA, which is
name-constrained to the swarm's own tree. A service hostname outside
it has no issuer in this deployment -- not a misconfiguration that
degrades, one that cannot produce a matching certificate at all.
Asserting it turns "your certs mysteriously don't work" into an eval
failure that names the option to edit. It applies to every
deployment, not only the autoconfigured one: an operator bringing
their own certificates still needs to know which names they are
bringing them for.
The message names the option rather than only the value, which is why
the hostnames are carried as (option, value) pairs and flattened into
serviceDomains afterwards -- flattening drops exactly the provenance
an error message needs.
Guarded on a null swarm.domain so hive-network.nix's required-domain
assertion stays the one that fires for that case.
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