set letter notifications to pending while notify-ftp does its stuff

this means that if the task is accidentally ran twice (eg we autoscale
notify-celery-worker-beat to 2), it won't send letters twice.

Additionally, update some function names and config variables to make
it clear that they are referring to letter jobs, rather than all letter
content

app/celery/scheduled_tasks.py

@@ -28,7 +28,9 @@ from app.dao.notifications_dao import (
     is_delivery_slow_for_provider,
     delete_notifications_created_more_than_a_week_ago_by_type,
     dao_get_scheduled_notifications,
-    set_scheduled_notification_to_processed)
+    set_scheduled_notification_to_processed,
+    dao_set_created_live_letter_api_notifications_to_pending,
+)
 from app.dao.statistics_dao import dao_timeout_job_statistics
 from app.dao.provider_details_dao import (
     get_current_provider,
@@ -325,21 +327,28 @@ def run_letter_jobs():
 @notify_celery.task(name="run-letter-notifications")
 @statsd(namespace="tasks")
 def run_letter_notifications():
-    notifications = dao_get_created_letter_api_notifications_that_dont_belong_to_jobs()
+    current_time = datetime.utcnow().isoformat()
+
+    notifications = dao_set_created_live_letter_api_notifications_to_pending()
 
     file_contents = create_dvla_file_contents_for_notifications(notifications)
+
+    file_location = '{}-dvla-notifications.txt'.format(current_time)
     s3upload(
         filedata=file_contents + '\n',
         region=current_app.config['AWS_REGION'],
-        bucket_name=current_app.config['DVLA_UPLOAD_BUCKET_NAME'],
-        file_location='2017-09-12-dvla-notifications.txt'
+        bucket_name=current_app.config['DVLA_BUCKETS']['notification'],
+        file_location=file_location
     )
 
-    # set noti statuses to pending or something
-
     notify_celery.send_task(
         name=TaskNames.DVLA_NOTIFICATIONS,
-        kwargs={'date': '2017-09-12'},
+        kwargs={'filename': file_location},
         queue=QueueNames.PROCESS_FTP
     )
-    current_app.logger.info("Queued {} ready letter job ids onto {}".format(len(notifications), QueueNames.PROCESS_FTP))
+    current_app.logger.info(
+        "Queued {} ready letter api notifications onto {}".format(
+            len(notifications),
+            QueueNames.PROCESS_FTP
+        )
+    )