A DDL change: the self-committing DDL transaction's structured effect (ADR-0003).
There is deliberately no statement-text field. Raw DDL SQL routinely embeds
literal values (DEFAULT 'secret', partition bounds) — a Rule 1 leak — so the
statement text is redacted before it reaches this struct, telemetry, or any log.
Only the structured schema/table/kind are exposed.
schema/table name the affected object; table is nil for schema-level DDL.
kind is the DDL kind as an atom (e.g. :alter_table, :create_table,
:drop_table, :truncate, :other). gtid is the self-committing DDL
transaction's own identity.