Investigate extrinsic_metadata journal client failing with incomplete entry

https://sentry.softwareheritage.org/organizations/swh/issues/10520/?referrer=phabricator_plugin

KeyError: 'id'
(9 additional frame(s) were not displayed)
...
  File "swh/indexer/cli.py", line 365, in journal_client
    client.process(worker_fn)
  File "swh/journal/client.py", line 318, in process
    batch_processed, at_eof = self.handle_messages(messages, worker_fn)
  File "swh/journal/client.py", line 356, in handle_messages
    worker_fn(dict(objects))
  File "swh/indexer/cli.py", line 362, in worker_fn
    fn(objects)
  File "swh/indexer/metadata.py", line 79, in process_journal_objects
    self.index(item["id"], data=RawExtrinsicMetadata.from_dict(item))

---

Migrated from T4412 (view on Phabricator)