add StatelessSession.getIdentifier() because repositories need it #4111

Job	Run time
Test with MariaDB	3m 22s
Test with MySQL	3m 57s
Run examples in 'session-example' on MySQL	1m 53s
Test with Java 17	3m 0s
Run examples in 'session-example' on PostgreSQL	1m 56s
Test with PostgreSQL	3m 10s
Test with Java 20	3m 1s
Test with MSSQLServer	3m 41s
Test with Java 21	3m 7s
Test with CockroachDB	5m 58s
Run examples in 'native-sql-example' on PostgreSQL	1m 49s
Test with Java 23	3m 28s
Test with Db2	5m 12s
Test with Oracle	4m 56s
Test with Java 24-ea	3m 22s
Test with Java 25-ea	3m 16s
	55m 8s

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