Docs: Add Person entity example to JDBC getting started section

[ruturajjadhav07]

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Summary

This PR improves the Getting Started with JDBC section of the documentation by adding the missing Person entity class to the example.
Previously, the docs showed PersonRepository, MyService, and ApplicationConfig without the corresponding entity, which could confuse new users.

By including the entity definition, the example is now self-contained and easier to follow.

Example Change

@Table("person")
public class Person {

    @Id
    private Long id;
    private String firstname;
    private String lastname;

    // getters and setters
}

[schauder]

This is merged.

Thanks for the contribution.

[ruturajjadhav07]

This is merged.

Thanks for the contribution.

Thanks, @schauder , for reviewing and merging this PR!
Glad to see the Person entity example included in the JDBC getting started section — it should make the documentation much clearer for new users.

Appreciate the polishing and final touches!