Added the random string reference to the letter

- uses the reference field on the notifications table to store a 16char random string used to cross reference DVLA letters back to the notification
- used as letter barcode does not have space for a UUID notification id

Depends on https://github.com/alphagov/notifications-utils/pull/149

Renamed the numeric_id to notification_reference in utils and changed validation rules to match this

Note also the persist_notification method set "reference" to be "client_reference" which is confusing and they are different things, so fixed this too.

app/__init__.py

@@ -1,4 +1,6 @@
 import os
+import random
+import string
 import uuid
 
 from flask import Flask, _request_ctx_stack
@@ -204,6 +206,10 @@ def create_uuid():
     return str(uuid.uuid4())
 
 
+def create_random_identifier():
+    return ''.join(random.choice(string.ascii_letters + string.digits) for _ in range(16))
+
+
 def process_user_agent(user_agent_string):
     if user_agent_string and user_agent_string.lower().startswith("notify"):
         components = user_agent_string.split("/")

app/celery/tasks.py

@@ -10,6 +10,7 @@ from notifications_utils.template import SMSMessageTemplate, WithSubjectTemplate
 from sqlalchemy.exc import SQLAlchemyError
 from app import (
     create_uuid,
+    create_random_identifier,
     DATETIME_FORMAT,
     notify_celery,
     encryption
@@ -262,7 +263,8 @@ def persist_letter(
             created_at=created_at,
             job_id=notification['job'],
             job_row_number=notification['row_number'],
-            notification_id=notification_id
+            notification_id=notification_id,
+            reference=create_random_identifier()
         )
 
         current_app.logger.info("Letter {} created at {}".format(saved_notification.id, created_at))
@@ -311,10 +313,8 @@ def create_dvla_file_contents(job_id):
         str(LetterDVLATemplate(
             notification.template.__dict__,
             notification.personalisation,
-            # This unique id is a 7 digits requested by DVLA, not known
-            # if this number needs to be sequential.
-            numeric_id=random.randint(1, int('9' * 7)),
-            contact_block=notification.service.letter_contact_block,
+            notification_reference=notification.reference,
+            contact_block=notification.service.letter_contact_block
         ))
         for notification in dao_get_all_notifications_for_job(job_id)
     )

app/notifications/process_notifications.py

@@ -36,6 +36,7 @@ def persist_notification(template_id,
                          job_id=None,
                          job_row_number=None,
                          reference=None,
+                         client_reference=None,
                          notification_id=None,
                          simulated=False):
     # if simulated create a Notification model to return but do not persist the Notification to the dB
@@ -53,7 +54,8 @@ def persist_notification(template_id,
         created_at=created_at or datetime.utcnow(),
         job_id=job_id,
         job_row_number=job_row_number,
-        client_reference=reference
+        client_reference=client_reference,
+        reference=reference
     )
     if not simulated:
         dao_create_notification(notification)

app/v2/notifications/post_notifications.py

@@ -47,7 +47,7 @@ def post_notification(notification_type):
                                         notification_type=notification_type,
                                         api_key_id=api_user.id,
                                         key_type=api_user.key_type,
-                                        reference=form.get('reference', None),
+                                        client_reference=form.get('reference', None),
                                         simulated=simulated)
     if not simulated:
         queue_name = 'priority' if template.process_type == PRIORITY else None