Store semesters for each student

[ArtemSBulgakov]

Currently it is hard to find out, in which semesters the student has participated. So, it's not possible to get some statistics over previous years.

There should be a mechanism to determine whether a student has took the course in specific semester, or not.

One idea is to create a separate table which will match a student with semester. Probably, it may also store the course of a student and medical group.

Some corner cases to deal with: students who were dropped for some period, and then became students again.

Important

The data structure is to be discussed