Create new task to build dvla file.

This will transform each notification in a job to a row in a file.
The file is then uploaded to S3.
The files will later be aggregated by the notifications-ftp app to send to dvla.

The method to upload the file to S3 should be pulled into notifications-utils package.
It is the same method used in notifications-admin.

app/config.py

@@ -175,6 +175,8 @@ class Config(object):
     FUNCTIONAL_TEST_PROVIDER_SERVICE_ID = None
     FUNCTIONAL_TEST_PROVIDER_SMS_TEMPLATE_ID = None
 
+    DVLA_UPLOAD_BUCKET_NAME = "{}-dvla-file-per-job".format(os.getenv('NOTIFY_ENVIRONMENT'))
+
 
 ######################
 # Config overrides ###