Task 1.3 of novox/hq ADR 0116. On AMQP an account was an HTTP call; on NATS
it is text the controller composes and the server reloads (ADR 0106). Pure,
so the mesh's whole authority model is testable as strings.
NATS closes a gap management.go recorded rather than hid: LavinMQ has no
topic permissions, so an emitter was granted the events exchange whole and
ADR 0042's origin reservation was "stamped by the sdk, not enforced here".
Per-subject permissions make it the server's refusal.
Two things found by composing a real file rather than reading the design:
- a scoped inbox leaves a responder unable to reply, because the answer goes
to the caller's inbox. allow_responses is the answer — one reply to the
subject of a message actually received — and only principals that serve
are granted it. Recorded in design 25 §4.
- composition must be deterministic: the module's entrypoint reloads on the
file's digest, so an order-dependent composer would reload the whole bus
on every controller restart. Covered by a test.
The golden fixture is the exact text `nats-server -t` accepts, so the syntax
is the server's rather than one we invented.
