Add @CreatedBy and @UpdatedBy annotation

[sdelamo]

See Entity Events

This PR adds the @CreatedBy and @UpdatedBy annotations to populate some entity fields automatically:

@MappedEntity
class Message {
    @Id
    @GeneratedValue
    @Nullable
    Long id

    @NotBlank
    String title

    @CreatedBy
    @Nullable
    String createdBy
}

[sdelamo]

@jeremyg484 I have started the PR, please pick it up from here and ping me when it is ready for review.

[sonarqubecloud]

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[sdelamo]

We will need to use the BeanIntrospection API.

[sdelamo]

@jeremyg484

One pending thought I have - should we ensure there is a means of mapping from/to full Principal objects of some sort the way that Spring Data does? (See https://docs.spring.io/spring-data/jpa/reference/auditing.html#auditing.annotations)

I think for now it is fine if we only allow a String as the type annotated with @CreatedBy @UpdatedBy. What the user wants to persist is a serialized representation of the user unique id. Mapping to a fully fledged Authentication may mean several queries to a database or a remote service.

Maybe what we need is an API to allow developers to calculate the user unique id in case they want to use other than Principal::getName

@FunctionalInterface
interface UserUniqueIdentifier {
@NonNull String uniqueIdentifier(@NonNull Principal principal);
}

and provide a default implementation.

@Secondary
@Singleton
interface DefaultUserUniqueIdentifier {
@NonNull 
String uniqueIdentifier(@NonNull  Principal principal) {
return principal.getName();
}
}