Function submitted_attainment_id 

pub fn submitted_attainment_id(
    student_number: &str,
    course_code: &str,
    enrolment_id: &str,
    attainment_date: NaiveDate,
    grade_scale_id: &str,
    grade_id: &str,
    credits: f64,
    attempt: u32,
) -> String

attempt distinguishes a legitimate re-submission from a replay of the same attempt, which reproduces the id.