:discard marks jobs as "discarded", i.e. jobs which permanently failed
due to e.g. exhausting all retries or explicitly being discared due to a
fatal error.
:cancel marks jobs as "cancelled" which does not imply failure.
While neither method counts as a job "exception" in the set of
telemetries we currently export via Prometheus, the different state
is visible in the (not-exported) metadata of oban job telemetry.
We can use handlers of those events to build bespoke statistics.
Ideally we'd like to distinguish in the receiver worker between
"invalid" and "already present or delete of unknown" documents,
but this is cumbersome to get get right with a list of
free-form, human-readable descriptions oof the violated constraints.
For now, just count both as an fatal error.
# but that is cumbersome to get right with a list of string error descriptions
by default just prevent job floods with a 1-seconds
uniqueness check, but override in RemoteFetcherWorker
for 5 minute uniqueness check over all states
:infinity is an option we can go for maybe at some point,
but that would prevent any refetches so maybe not idk.
