A queued job delivered to a processor.
data: T
The job payload.
Transport headers carried with the job, mirroring
MessageMetadata.headers so the two ingresses cannot drift on
meaning: {} means the channel was read and carried nothing; absent
means there was no channel.
This is the queue's half of trace propagation. A framework with a
CAPABILITIES.TELEMETRY provider writes a W3C traceparent here when the
job is enqueued, so the processor's work joins the trace of the request
that caused it; without one, the map holds only what the caller passed in
AddJobOptions.headers.
Absent is a real answer and never substituted with {}: an IQueue
implementation whose transport cannot carry a header omits the member
rather than reporting an empty one, so "this queue has no channel" stays
distinguishable from "the channel was empty".