Support embedded and related SQL attributes

[Evolvion]

Summary

• Detect owned child tables and expose them as scalar or embedded object-class attributes.
• Add transactional create, update, and delete handling for related rows.
• Resolve child and junction relationships using their declared parent and target columns, including non-UID and composite joins.
• Centralize metadata-aware QueryDSL table access shared by read and write paths.
• Keep junction references read-only and remove their rows safely when deleting the parent.
• Extend the shared database contract for H2, PostgreSQL, SQLite, Oracle, MariaDB, and MySQL.

Oracle JDBC does not expose foreign keys referencing non-primary unique keys through DatabaseMetaData, so that capability is explicitly represented in the database test configuration.

Testing

• mvn test — 372 tests passed
• Six-database contract suite — 108 tests passed, no failures or skips

Work package

#12110