Use indexing events to update the status of the release workflow

[thatbudakguy]

For discussion and previous work on the underlying problem, see sul-dlss/argo#3893.

As discussed at storytime on 3/11, we would like to try using the events currently published from the Searchworks and Earthworks indexers via dor-event-client to update the status of the release workflow. Specifically, several kinds of events are currently published:

• indexing_success, for when an item was added to or updated in the Searchworks or Earthworks index
• indexing_deleted, for when an item was removed from the Seachworks or Earthworks index
• indexing_skipped, for when the indexer did not process an item (e.g. because of bad metadata)
• indexing_errored, for when the indexer raised an error during indexing

These events are currently sent by the indexer after items are released via the releaseWF in Argo and processed via purl-fetcher's queue. We would like to use the indexing status of an item to update the release workflow, so that the workflow is only considered "completed" once a message is received from the indexer.

Edge cases to consider:

• "managed PURLs", a 1:1 correspondence between an SDR object and a FOLIO record where the release is controlled via updating the record in FOLIO, and a link to the object is inserted into the MARC 856 field at index time
• "free-range PURLs", a looser correspondence between a FOLIO record and an SDR object that is related to it in some way, where the 856 field is not managed automatically by the indexer (there are only a few hundred such objects)

Note that the Searchworks indexer does not currently report any events to SDR when FOLIO records are changed, although this could be implemented.