fix: Add GenerationType and Transactional annotations

[cchacin]

Add missing annotations required for the examples to work properly:

• @GeneratedValue(strategy = GenerationType.IDENTITY) for auto-incremental id
• @Transactional for the DELETE endpoint to work

[ttelang]

• @GeneratedValue(strategy = GenerationType.IDENTITY) for auto-incremental id

In this tutorial, we intentionally use @GeneratedValue without an explicit strategy:

@Id
@GeneratedValue
private Long id;

This is equivalent to GenerationType.AUTO and delegates the decision to the Jakarta Persistence provider (Hibernate/OpenJPA/etc.), which selects the most suitable mechanism for the configured database.

The provider defaults are as below:

• SEQUENCE for DBs that support sequences (PostgreSQL/Oracle)
• IDENTITY for auto-increment DBs (MySQL/MariaDB)
• TABLE as a fallback where sequences/identity are unavailable

This choice improves the portability of the tutorial because the same examples can run across different databases without forcing an ID strategy that may not exist.

[ttelang]

In this tutorial, we intentionally use @GeneratedValue without an explicit strategy:

@Id
@GeneratedValue
private Long id;

This is equivalent to GenerationType.AUTO and delegates the decision to the Jakarta Persistence provider (Hibernate/OpenJPA/etc.), which selects the most suitable mechanism for the configured database.

The provider defaults are as below:

• SEQUENCE for DBs that support sequences (PostgreSQL/Oracle)
• IDENTITY for auto-increment DBs (MySQL/MariaDB)
• TABLE as a fallback where sequences/identity are unavailable

This choice improves the portability of the tutorial because the same examples can run across different databases without forcing an ID strategy that may not exist.

I would add the above explanation as a note in the README.adoc file via a separate PR so that other developer understand why no explicit strategy was mentioned.

[ttelang]

• @Transactional for the DELETE endpoint to work

@Transactional was not used, as this implementation uses in-memory implementation. You are also right; as an enterprise best practice, I should have used @transactional for all mutating operations, as the intent here is to move to the database going forward.

I would be updating the code via a separate PR at appropriate places.

[ttelang]

Add missing annotations required for the examples to work properly:

• @GeneratedValue(strategy = GenerationType.IDENTITY) for auto-incremental id
• @Transactional for the DELETE endpoint to work

The examples have been tested thoroughly and are working properly without these annotations.

See my earlier comments for an explanation of why the above annotations was not added in the code examples.