agendas: fix export/import of TimePeriodException (#24152)

- convert datetime to naive before serialization,
- export missing fields: external_id, recurrence_id and update_datetime.

chrono/agendas/models.py

@@ -622,15 +622,25 @@ class TimePeriodException(models.Model):
 
     @classmethod
     def import_json(cls, data):
-        data['start_datetime'] = make_aware(datetime.datetime.strptime(
-            data['start_datetime'], '%Y-%m-%d %H:%M:%S'))
-        data['end_datetime'] = make_aware(datetime.datetime.strptime(
-            data['end_datetime'], '%Y-%m-%d %H:%M:%S'))
+        def import_datetime(s):
+            '''Import datetime as a naive ISO8601 serialization'''
+            return make_aware(datetime.datetime.strptime(s, '%Y-%m-%d %H:%M:%S'))
+
+        for k, v in data.items():
+            if k.endswith('_datetime'):
+                data[k] = import_datetime(v)
         return cls(**data)
 
     def export_json(self):
+        def export_datetime(dt):
+            '''Export datetime as a naive ISO8601 serialization'''
+            return make_naive(dt).strftime('%Y-%m-%d %H:%M:%S')
+
         return {
             'label': self.label,
-            'start_datetime': self.start_datetime.strftime('%Y-%m-%d %H:%M:%S'),
-            'end_datetime': self.end_datetime.strftime('%Y-%m-%d %H:%M:%S'),
+            'start_datetime': export_datetime(self.start_datetime),
+            'end_datetime': export_datetime(self.end_datetime),
+            'external_id': self.external_id,
+            'recurrence_id': self.recurrence_id,
+            'update_datetime': export_datetime(self.update_datetime),
         }