doorcontrol: Grant instructors access for ~1 hour around their class times

Also the required foundation for #14

doorcontrol/tasks/update_doors.py

@@ -1,7 +1,10 @@
 import dataclasses
 import logging
+from datetime import timedelta
 from typing import TypedDict
 
+from django.utils import timezone
+
 from django_q.tasks import async_task
 
 from cmsmanage.django_q2_helper import q_task_group
@@ -62,6 +65,17 @@ class DoorMember:
                 if getattr(member, attribute_rule.access_field)
             }
 
+        # grant instructors access for ~1 hour around their class times
+        if hasattr(member, "eventinstructor") and getattr(member, door.access_field):
+            now = timezone.now()
+            margin = timedelta(hours=1)
+            if member.eventinstructor.eventext_set.filter(
+                occurred=True,
+                meeting_times__start__lt=now + margin,
+                meeting_times__end__gt=now - margin,
+            ).exists():
+                reasons_and_schedules["Instructor for Active Class"] = "Unlimited"
+
         reasons = sorted(reasons_and_schedules.keys())
 
         return cls(