Add inheritance module: SINGLE_TABLE vs JOINED vs TABLE_PER_CLASS on Hibernate 7.4.13.Final

Same payment hierarchy mapped three ways plus @MappedSuperclass, run with plain Hibernate on H2.
Tests assert and write the generated DDL, the INSERT/SELECT SQL, row/insert/FK/nullability counts and
the three failures (NOT NULL on a SINGLE_TABLE subclass column, IDENTITY with TABLE_PER_CLASS, querying a
@MappedSuperclass); Bench writes indicative polymorphic-query timings. No docs folder: depth lives in the post.

inheritance/output/01-ddl-single-table.txt

@@ -0,0 +1,33 @@
+-- DDL generated by Hibernate 7.4.13.Final for H2, strategy SINGLE_TABLE
+-- tables created: 2
+
+
+    create sequence st_order_seq start with 1 increment by 50;
+
+    create sequence st_payment_seq start with 1 increment by 50;
+
+    create table st_order (
+        id bigint not null,
+        payment_id bigint not null,
+        reference varchar(20) not null,
+        primary key (id)
+    );
+
+    create table st_payment (
+        amount numeric(12,2) not null,
+        card_last4 varchar(4),
+        currency varchar(3) not null,
+        id bigint not null,
+        bank_code varchar(11),
+        payment_type varchar(12) not null check ((payment_type in ('CARD','BANK','WALLET'))),
+        network varchar(16),
+        provider varchar(24),
+        iban varchar(34),
+        primary key (id),
+        constraint st_payment_subclass_columns check ((payment_type <> 'CARD' or card_last4 is not null) and (payment_type <> 'BANK' or iban is not null) and (payment_type <> 'WALLET' or provider is not null))
+    );
+
+    alter table if exists st_order 
+       add constraint FKdi3y406uyk3cm6po29lmjirt5 
+       foreign key (payment_id) 
+       references st_payment;