Fix FDP v2 index API

[dennisvang]

Changes:

• Replaced last occurrences of registrationTime, modificationTime, and lastRetrievalTime, by createdAt, updatedAt, and lastRetrievalAt, respectively, conforming to changes made in Migrate to PostgreSQL #519
• Added IndexEntry.events to specify cascading and orphan removal
• Added tests to reproduce issues mentioned below
• Set IndexEntry.lastRetrievalAt in EventService.processMetadataRetrieval and in test fixture
• Added a rudimentary validation of sort url query parameters

This fixes the following:

• fixes FDP v2 index GET index/entries fails on sort #633
• fixes FDP v2 index lastRetrievalTime (or lastRetrievalAt) not set #640
• fixes FDP v2 index GET index/entries/{uuid} fails #643
• fixes FDP v2 index DELETE index/entries/{uuid} fails #644

[dennisvang]

The error Cannot invoke "java.time.Instant.isAfter(java.time.Instant)" because "lastRetrievalAt" is null still persists.
Also see #633 (comment)

sub-issue:

• FDP v2 index lastRetrievalTime (or lastRetrievalAt) not set #640

[dennisvang]

Now we can click FDP links and delete FDPs, but we get the following after "Trigger ping":

...
2025-03-05 17:20:35,295 271938 [fdp-task-3] WARN  org.hibernate.engine.jdbc.spi.SqlExceptionHelper - SQL Error: 0, SQLState: 23503
2025-03-05 17:20:35,296 271939 [fdp-task-3] ERROR org.hibernate.engine.jdbc.spi.SqlExceptionHelper - ERROR: insert or update on table "index_event" violates foreign key constraint "fk__index_event_triggered_by"
  Detail: Key (triggered_by)=(50884866-6eb4-4562-b500-a31d83226a32) is not present in table "index_event".
2025-03-05 17:20:35,298 271941 [fdp-task-3] ERROR org.fairdatapoint.service.index.event.EventService - Failed to retrieve metadata: could not execute statement [ERROR: insert or update on table "index_event" violates foreign key constraint "fk__index_event_triggered_by"
  Detail: Key (triggered_by)=(50884866-6eb4-4562-b500-a31d83226a32) is not present in table "index_event".] [insert into index_event (created_at,executed_at,finished_at,payload,related_to,remote_addr,triggered_by,type,updated_at,version,uuid) values (?,?,?,?,?,?,?,?,?,?,?)]; SQL [insert into index_event (created_at,executed_at,finished_at,payload,related_to,remote_addr,triggered_by,type,updated_at,version,uuid) values (?,?,?,?,?,?,?,?,?,?,?)]; constraint [fk__index_event_triggered_by]
2025-03-05 17:20:35,298 271941 [fdp-task-3] INFO  org.fairdatapoint.service.index.event.EventService - Finished metadata retrieval triggered by 50884866-6eb4-4562-b500-a31d83226a32

UPDATE: forgot to initialize the IndexEntry.events set.

[MarekSuchanek]

Looks great 👍🏻