chore(tutorial): granting qualification automatically picks better expiry date
Previously, the form for granting tutorial users a qualification suggested the minimum of all expiry dates, if there where several course qualficiations. This lead to some users being granted driving licences being valid for only one month.
The expiry date can now be left blank, using the validDuration of the selected qualification instead.
The default is blank, if there are more than one course qualification having disagreeing qualification dates.