Add endpoint for getting / creating a hidden template

We want a way of getting the hidden precompiled template from admin,
so this adds an endpoint which gets the template or creates it if it doesn't
exist. The function to get or create the hidden template already existed
but has been moved to the template DAO now that it is used in more
places.

app/v2/notifications/post_notifications.py

@@ -11,11 +11,9 @@ from app.celery.research_mode_tasks import create_fake_letter_response_file
 from app.clients.document_download import DocumentDownloadError
 from app.config import QueueNames, TaskNames
 from app.dao.notifications_dao import update_notification_status_by_reference
-from app.dao.templates_dao import dao_create_template
-from app.dao.users_dao import get_user_by_id
+from app.dao.templates_dao import get_precompiled_letter_template
 from app.letters.utils import upload_letter_pdf
 from app.models import (
-    Template,
     SMS_TYPE,
     EMAIL_TYPE,
     LETTER_TYPE,
@@ -27,7 +25,6 @@ from app.models import (
     NOTIFICATION_SENDING,
     NOTIFICATION_DELIVERED,
     NOTIFICATION_PENDING_VIRUS_CHECK,
-    SECOND_CLASS
 )
 from app.notifications.process_letter_notifications import (
     create_letter_notification
@@ -342,28 +339,3 @@ def get_reply_to_text(notification_type, form, template):
         reply_to = template.get_reply_to_text()
 
     return reply_to
-
-
-def get_precompiled_letter_template(service_id):
-    template = Template.query.filter_by(
-        service_id=service_id,
-        template_type=LETTER_TYPE,
-        hidden=True
-    ).first()
-    if template is not None:
-        return template
-
-    template = Template(
-        name='Pre-compiled PDF',
-        created_by=get_user_by_id(current_app.config['NOTIFY_USER_ID']),
-        service_id=service_id,
-        template_type=LETTER_TYPE,
-        hidden=True,
-        subject='Pre-compiled PDF',
-        content='',
-        postage=SECOND_CLASS
-    )
-
-    dao_create_template(template)
-
-    return template