Populate collection membership database by reading from queue

[thatbudakguy]

Once #562 is complete, we need to make sure that the database that powers the /collections/:druid/purls endpoint is updated based on up-to-date information from the queue. Exhibits uses this endpoint to figure what items to index when a curator wants to index an entire collection.

For an example of logic that reads from Kafka, see searchworks-traject-indexer's KafkaPurlFetcherReader and note that our current kafka client is EOL (sul-dlss/searchworks_traject_indexer#737).

[thatbudakguy]

Is this done? It looks to me like the PurlCocinaUpdater service dutifully updates the database records, including collection membership, when purls are updated.

[jcoyne]

I think it is