Change get_bucket_name_and_prefix_for_notification to use created_at

The `get_bucket_name_and_prefix_for_notification` function was looking
at the `sent_at` or `updated_at` at time of a notification to see which
bucket it was in. Precompiled letters sent through the admin app don't
have either of these times - they only have a `created_at` time, so this
lets the function check `created_at` time too.

app/letters/utils.py

@@ -63,8 +63,10 @@ def get_bucket_name_and_prefix_for_notification(notification):
         bucket_name = current_app.config['LETTERS_PDF_BUCKET_NAME']
         if notification.sent_at:
             folder = "{}/".format(notification.sent_at.date())
-        else:
+        elif notification.updated_at:
             folder = get_folder_name(notification.updated_at, False)
+        else:
+            folder = get_folder_name(notification.created_at, False)
 
     upload_file_name = PRECOMPILED_BUCKET_PREFIX.format(
         folder=folder,

tests/app/letters/test_letter_utils.py

@@ -68,6 +68,20 @@ def test_get_bucket_name_and_prefix_for_notification_get_from_sent_at_date(sampl
     ).upper()
 
 
+def test_get_bucket_name_and_prefix_for_notification_from_created_at_date(sample_notification):
+    sample_notification.created_at = datetime(2019, 8, 1, 12, 00)
+    sample_notification.updated_at = datetime(2019, 8, 2, 12, 00)
+    sample_notification.sent_at = datetime(2019, 8, 3, 12, 00)
+
+    bucket, bucket_prefix = get_bucket_name_and_prefix_for_notification(sample_notification)
+
+    assert bucket == current_app.config['LETTERS_PDF_BUCKET_NAME']
+    assert bucket_prefix == '{folder}/NOTIFY.{reference}'.format(
+        folder='2019-08-03',
+        reference=sample_notification.reference
+    ).upper()
+
+
 @freeze_time(FROZEN_DATE_TIME)
 def test_get_bucket_name_and_prefix_for_notification_precompiled_letter_using_test_key(
     sample_precompiled_letter_notification_using_test_key