False negatives in eligibility

[ShootingStar91]

• Sometimes student does not have rights at all to the page, and they will have a row in database with studentnumber missing, this seems to happen when they have previously been an employee before having a studentnumber. Possibly headers from Shibboleth are missing the studentnumber
• Possibly earlier JOO-studyright via another university block eligibility even though it should not
• Absence issue: eligibility checker doesn't distinguish between postponing and absence #156