Description

Expand the DDL builder to support Foreign Keys via the .References\ clause (ESP-035).

Context

Following ESP-034, Foreign Keys are essential for referential integrity.

Acceptance criteria

• Method .References\ available in DDL column builders.
• \CREATE TABLE\ correctly serializes \REFERENCES T(C)\ for Firebird.
• \CREATE TABLE\ correctly serializes \REFERENCES T(C)\ for PostgreSQL.
• \ALTER TABLE ADD COLUMN\ correctly includes the \REFERENCES\ clause.
• All unit tests pass.