Add notifications property to person entity

* There is now an enum for different kinds of mail notifications.

* Each person has a list of mail notifications configured.
  Add database changelog to create table `Person_notifications`,
  insert notifications for each person dependent on their permissions.

* refs #18005
Adjust mail service to get boss and office members by notification type

* Instead of fetching bosses and office members by role, fetch them by
  notification type.

* NOTE: User notification type has no effect in mail service for now.

* refs #18005
Adjust notifications table changelog to h2 demands

* refs #18005
Include notification options in person form

* refs #18005
Hide user notification option in person form

* For now it's obligatory that every user gets mail notifications about
  the progress of their applications for leave.
  At the moment the user notification type has no effect in mail
  service.

* refs #18005
Test data creation: add mail notifications for test persons

* refs #18005
Add validation for mail notification options

* If selecting boss or office mail notification then the according role
  must be set too.

* refs #18005