Unify API of lesson period with event and extra lesson by adding properties for group names

aleksis/apps/chronos/models.py

@@ -473,6 +473,16 @@ class LessonPeriod(WeekAnnotationMixin, TeacherPropertiesMixin, ExtensibleModel)
     def get_groups(self) -> models.query.QuerySet:
         return self.lesson.groups
 
+    @property
+    def group_names(self):
+        """Get group names as joined string."""
+        return self.lesson.group_names
+
+    @property
+    def group_short_names(self):
+        """Get group short names as joined string."""
+        return self.lesson.group_short_names
+
     def __str__(self) -> str:
         return f"{self.period}, {self.lesson}"