Update `Person` ID type from `long` to `Long`

[Voodooa]

Hello,

In the guide "[Accessing JPA Data with REST](https://github.com/spring-guides/gs-accessing-data-rest/blob/main/complete/src/main/java/com/example/accessingdatarest/Person.java)," the Person entity uses an ID of type long.

To align this guide with JPA best practices and other Spring examples (where Long is used for IDs), I suggest changing long to Long. This prevents issues related to the default value of long (0, which may be interpreted as a valid ID) and ensures better consistency across examples.

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Proposed Fix:

@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id; // Change from long to Long

Thank you for considering this update.