feat: store and update last_visit in person model

app/base/models/course_visit.py

@@ -33,3 +33,39 @@ class CourseVisit(models.Model):
 
     def get_absolute_url(self):
         return reverse('course-visit:detail', kwargs={'pk': self.pk})
+
+    def save(self, *args, **kwargs):
+        # update last_visit time of all involved persons
+        old_date: 'date|None' = None
+        old_list: 'list[Person]' = []
+
+        if self.pk:
+            prev = CourseVisit.objects.get(pk=self.pk)
+            old_date = prev.date
+            old_list.append(prev.participant)
+            if prev.teacher:
+                old_list.append(prev.teacher)
+
+        rv = super().save(*args, **kwargs)
+
+        new_date = self.date
+        new_list: 'list[Person]' = [self.participant]
+        if self.teacher:
+            new_list.append(self.teacher)
+
+        for person in old_list:
+            if person not in new_list:
+                person.update_last_visit(None)
+        for person in new_list:
+            if person not in old_list or old_date != new_date:
+                person.update_last_visit(new_date)
+
+        return rv
+
+    def delete(self, *args, **kwargs):
+        rv = super().delete(*args, **kwargs)
+        # update last_visit time of all involved persons
+        self.participant.update_last_visit(None)
+        if self.teacher:
+            self.teacher.update_last_visit(None)
+        return rv