Oban-job-enqueue transport.

Eliminates the "two-channel dance" where a producer dispatches an AshDispatch event for observability AND separately calls MyWorker.new(args) |> Oban.insert/1 for the side-effect work. With this transport, the producer dispatches once; the event declaration carries the worker + unique-keys in :metadata, and the dispatcher enqueues the worker as one of the event's channels.

Channel config

[transport: :oban, audience: :system]

Event metadata

event :my_event,
  channels: [
    [transport: :broadcast, audience: :admin],
    [transport: :oban,      audience: :system]
  ],
  metadata: [
    oban_worker: MyApp.Workers.DoTheThing,
    # Optional. When present, passed to `MyApp.Workers.DoTheThing.new/2`
    # as `unique: [keys: <oban_unique_keys>]`. Use to dedupe enqueues
    # on a subset of args (e.g. `[:entry_id]`).
    oban_unique_keys: [:entry_id]
  ]

The job args are context.data (the third argument to Dispatcher.dispatch/3) with string keys (Oban requires JSON-serializable args; the dispatcher stringifies atom keys here so producers can keep idiomatic atom keys in their dispatch payloads).

Lightweight (no receipt)

Like :broadcast, this transport is lightweight — no DeliveryReceipt row is created (the enqueued oban_jobs row IS the audit trail). Producers who want a receipt should pair :oban with another transport on the same event.

Failure semantics

• Missing oban_worker in metadata → logs a warning, returns {:ok, receipt} with skipped: "missing_oban_worker". The other channels still deliver. Treats configuration drift as a soft-fail rather than crashing producers.
• Oban.insert/1 returns {:error, _} → logs at :error, propagates as {:error, reason} (the dispatcher swallows per-channel errors so other channels keep delivering — matches the email/discord/slack precedent).
• Oban unavailable / not started → caught by the rescue; returns {:error, exception} per the same precedent.

Status

Single consumer at ship time: Mosis (sibling repo). Extend as needed — same shape as the receipt-skip channels.