process letters from api traffic

there are three steps to this

1. Create a job
  * Starts in status 'ready to send'
  * Created by None, since it's from the API
  * original file name 'letter submitted via api'
2. Create a single notification for that job
  * job_row_number 0
  * client reference if provided
  * address line 1 as recipient
3. Trigger the build_dvla_file task
  we know that all the notifications have been created for this job
  (since we just created them ourselves synchronously), so this will
  just create the dvla-format file for the job, and upload it to s3.

app/notifications/process_letter_notifications.py

@@ -0,0 +1,41 @@
+from app import create_random_identifier
+from app.models import LETTER_TYPE, JOB_STATUS_READY_TO_SEND
+from app.notifications.process_notifications import persist_notification
+
+
+def create_letter_api_job(template):
+    service = template.service
+    if not service.active:
+        raise InvalidRequest('Create job is not allowed: service is inactive', 403)
+    if template.archived:
+        raise InvalidRequest('Create job is not allowed: template is deleted', 400)
+
+
+    job = Job(
+        original_file_name='letter submitted via api',
+        service=service,
+        template=template,
+        template_version=template.version,
+        notification_count=1,
+        job_status=JOB_STATUS_READY_TO_SEND,
+        created_by=None
+    )
+    dao_create_job(job)
+
+
+def create_letter_notification(letter_data, job, api_key):
+    notification = persist_notification(
+        template_id=job.template.id,
+        template_version=job.template.version,
+        recipient=letter_data['personalisation']['address line 1'],  # or addressline1 or address_line_1?
+        service=job.service,
+        personalisation=letter_data['personalisation'],
+        notification_type=LETTER_TYPE,
+        api_key_id=api_key.id,
+        key_type=api_key.key_type,
+        job_id=job.id,
+        job_row_number=0,
+        reference=create_random_identifier(),
+        client_reference=letter_data.get('reference')
+    )
+    return notification