Projections require Entity Id field to not throw exception while instantiating

Issue Description

When creating interface projections that only expose specific fields (closed projections), omitting the entity's @Id field can result in runtime errors during proxy creation, even when the projected fields contain valid non-null data.

Entity

@Data
@Builder
@Table("file")
public class File {
    @Id
    private Long id;
    private String fileId;
    private Long uploaderId;
    private LocalDateTime uploadDate;
    private String fullName;
    @Builder.Default
    @MappedCollection(idColumn = "file_id")
    private Set<Document> documents = new HashSet<>();
}

Projection

public interface FilePreview {
    String getFileId();
    LocalDateTime getUploadDate();
}

Repository

public interface FileRepository extends CrudRepository<File, Long> {
    List<FilePreview> findBy();
}

When invoking findBy an java.lang.IllegalStateException is thrown with message Identifier value must not be null at this point.

Modifying the projection to

public interface FilePreview {
    Long getId();
    String getFileId();
    LocalDateTime getUploadDate();
}

results in the method not throwing exception.

The documentation does not mention anywhere this as an intended behaviour and it's not clear why would it be needed.