fix: Investigate simultaneous updates of data values is not updating at all [ DHIS2-16080 ]

[lucaCambi77]

https://dhis2.atlassian.net/browse/DHIS2-16080

In the old tracker, we have the /events endpoint:
@PutMapping(value = "/{uid}/{dataElementUid}"
which is supposed to update the event data values although it goes through the generic event update.

There are 2 points about this issue:
1- With the WorkContextLoader, info about the existing eventdatavalues field is preloaded. Therefore, if we have a concurrent update we might preload data element values that are no longer valid
2- Apparently, using the spring JdbcTemplate batchUpdate the concurrency and wait for the same row update is not working.

Solution - Relying on @Transactional

One possible solution to this issue is to process one data element value at a time inside the JSON.
This is done using the Postgres function jsonb_update or jsonb_insert.
@Transactional should handle the concurrency for us if we use hibernate queries.

Alternative solution

An alternative approach to this issue is to use locking. There are 2 possible locking we can use:

• Optimistic locking: hibernate recommends we use the @Version field so we can catch if the row we are updating is the current version or not. This can have a big impact on the current state of the event table
• Pessimistic locking. This will eventually result in using the SELECT .. FOR UPDATE syntax which can slow down performances and create deadlocks

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