add description length to room admin list

shiftregister/app/admin.py

@@ -3,7 +3,15 @@ from django.contrib.admin import DateFieldListFilter
 
 from .models import Room, Shift, Helper, ShiftRegistration, Message, LoginToken
 
-admin.site.register(Room)
+
+@admin.register(Room)
+class RoomAdmin(admin.ModelAdmin):
+    list_display = ("name", "description_length")
+
+    def description_length(self, object):
+        if object.description:
+            return len(object.description)
+        return 0
 
 
 @admin.register(Shift)