hive-ci and hive-forge both bind the runtime-generated hive CA cert
read-only and order their container@ unit after hive-tls-ca.service so
the bind source exists before nspawn sets the mount up — the same
bind-mount + ordering + rationale duplicated verbatim in two modules.
Extract that language-agnostic half into a pure helper,
nix/host-modules/lib/hive-ca-trust.nix, taking a container name and
returning { useSelfSigned, caContainerPath, bindMount, containerOrdering }.
The per-runtime consumption stays at each call site (hive-ci's additive
NODE_EXTRA_CA_CERTS, hive-forge's Go SSL_CERT_FILE concat). hive-ci folds
containerOrdering into its existing mkMerge alongside the TimeoutStartSec
bump.
The helper is a pure function, not a module: host-modules/default.nix is
an explicit aggregator (not a glob) and the docs eval imports that same
aggregator, so the lib/ file is never picked up as a module. A third
outbound-TLS-trusting container no longer means a third copy-paste.
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