For optimistic locking fix upsert, implement updateBatch

Upsert using INSERT ... ON CONFLICT (id) DO UPDATE fails because the INSERT trigger overwrites the _version property that the UPDATE trigger uses to detect optimistic locking conflicts.

Solution:

Implement upsert using a transaction and executing two SQL commands:

UPDATE ...;
IF NOT FOUND THEN INSERT ...;

Adding updateBatch allows to replace upsertBatch depending on the use case: insertBatch or updateBatch. When optimistic locking is enabled the client must know in advance whether it is insert or update.