Support "student group" field of lesson

Untis has a StudentGroups table, containing an Untis-style composite key, Name, SUBJECT_ID and comma-separated ClassIds:

+-----------+---------------+------------+-----------------+---------+---------+---------+-----------+----------------+----------+------------+---------+------------+----------+----------------------+
| SCHOOL_ID | SCHOOLYEAR_ID | VERSION_ID | STUDENTGROUP_ID | Counter | USER_ID | Deleted | Name      | StatisticCodes | Longname | ForeignKey | OldName | SUBJECT_ID | ClassIds | BASE_STUDENTGROUP_ID |
+-----------+---------------+------------+-----------------+---------+---------+---------+-----------+----------------+----------+------------+---------+------------+----------+----------------------+
|     65535 |      20222023 |          1 |             176 |       4 |       1 |       0 | PH_Q1_MOE | NULL           | NULL     | NULL       | NULL    |         46 | ,8,      |                    0 |
+-----------+---------------+------------+-----------------+---------+---------+---------+-----------+----------------+----------+------------+---------+------------+----------+----------------------+

In the Lesson table, we find the string in the LessonElement column as well, e.g.:

54~0~46~51;~0;~0~0~83906~~~~~"PH1"~~~n~~;8;~"PH_Q1_MOE"~~176~0~154800~0~0~~70800~

I am unsure whether we should only use the string in the Lesson table, or actually go and import the StudentGroups first into AlekSIS. They seem to have helpful information, because they carry the parent group IDs as ClassIds. I have no idea how that can be matched back to Qi or whatever…