Avoid setting the slot duration at import

Addresses #14 (closed)

AKModel/models.py

@@ -415,7 +415,7 @@ class Event(models.Model):
             end_timeslot = timeslot_dict[max(scheduled_slot["timeslot_ids"])].avail
             solver_duration = (end_timeslot.end - start_timeslot.start).total_seconds() / 3600.0
 
-            if solver_duration + 1e-4 < slot.duration:
+            if solver_duration + 2e-4 < slot.duration:
                 raise ValueError(
                     _(
                         "Duration of AK {ak_name} assigned by solver ({solver_duration} hours) "