Add score and categorization to student's attributes.

[aykborstelmann]

Supplementation of #4:

Add score as well later in #7 the categorization to the student's attributes.

This may be accomplished by

@Entity
public class Student {
    
    private String firstName;
    ...

    public Integer score() {
        // method call to student controller.
    }

}

Also, it would be great to have a link to /students/{id}/score in the _links-section of a student.

So to wrap it up:

• Add categorization and score to the student's attributes directly
• Add a link to categorization and score in the _links-section of a student

This would be comfortable to work with.