Make Absence model real, usable calendar event by adding mandatory value methods

aleksis/apps/kolego/models/absence.py

 from django.db import models
+from django.db.models import QuerySet
+from django.http import HttpRequest
 from django.utils.translation import gettext_lazy as _
 
 from colorfield.fields import ColorField
@@ -80,6 +82,32 @@ class Absence(FreeBusy):
 
     comment = models.TextField(verbose_name=_("Comment"), blank=True)
 
+    @classmethod
+    def get_objects(
+        cls, request: HttpRequest | None = None, params: dict[str, any] | None = None
+    ) -> QuerySet:
+        qs = super().get_objects(request, params).select_related("person", "reason")
+        if params:
+            if params.get("person"):
+                qs = qs.filter(person_id=params["person"])
+            elif params.get("persons"):
+                qs = qs.filter(person_id__in=params["persons"])
+            elif params.get("group"):
+                qs = qs.filter(person__member_of__id=params.get("group"))
+        return qs
+
+    @classmethod
+    def value_title(cls, reference_object: "Absence", request: HttpRequest | None = None) -> str:
+        """Return the title of the calendar event."""
+        return f"{reference_object.person} ({reference_object.reason})"
+
+    @classmethod
+    def value_description(
+        cls, reference_object: "Absence", request: HttpRequest | None = None
+    ) -> str:
+        """Return the title of the calendar event."""
+        return ""
+
     def __str__(self):
         return f"{self.person} ({self.datetime_start} - {self.datetime_end})"