Serialise template immediately after fetching

This commit changes the code in post notification endpoint to handle a
serialised template (ie a `dict`) rather than a database object.

This is the first step towards being able to cache the template and not
hit the database on every request.

There should be no functional changes here, it’s just refactoring.

There are some changes to the tests where the signature of functions
has changed.

Importing of the template schema has to be done at a function level,
otherwise Marshmallow gets weird.

This commit also copies the `JSONModel` class from the admin app, which
turns serialised data (a dict made from JSON) into an object on which
certain predefined properties are allowed.

This means we can still do the caching of serialised data, without
having to change too much of the code in the app, or make it ugly by
sprinkling dict lookups everywhere.

We’re not copying all of JSONModel from the admin app, just the bits we
need. We don’t need to compare or hash these objects, they’re just used
for lookups. And redefining `__getattribute__` scares Leo.

app/v2/notifications/post_notifications.py

@@ -98,14 +98,13 @@ def post_precompiled_letter_notification():
         'address_line_1': 'Provided as PDF'
     }
 
-    reply_to = get_reply_to_text(LETTER_TYPE, form, template)
-
     notification = process_letter_notification(
         letter_data=form,
         api_key=api_user,
+        service=authenticated_service,
         template=template,
         template_with_content=None,  # not required for precompiled
-        reply_to_text=reply_to,
+        reply_to_text='',  # not required for precompiled
         precompiled=True
     )
 
@@ -147,6 +146,7 @@ def post_notification(notification_type):
         notification = process_letter_notification(
             letter_data=form,
             api_key=api_user,
+            service=authenticated_service,
             template=template,
             template_with_content=template_with_content,
             reply_to_text=reply_to
@@ -156,7 +156,8 @@ def post_notification(notification_type):
             form=form,
             notification_type=notification_type,
             api_key=api_user,
-            template=template_with_content,
+            template=template,
+            template_with_content=template_with_content,
             template_process_type=template.process_type,
             service=authenticated_service,
             reply_to_text=reply_to
@@ -166,7 +167,15 @@ def post_notification(notification_type):
 
 
 def process_sms_or_email_notification(
-    *, form, notification_type, api_key, template, template_process_type, service, reply_to_text=None
+    *,
+    form,
+    notification_type,
+    api_key,
+    template,
+    template_with_content,
+    template_process_type,
+    service,
+    reply_to_text=None,
 ):
     notification_id = uuid.uuid4()
     form_send_to = form['email_address'] if notification_type == EMAIL_TYPE else form['phone_number']
@@ -186,19 +195,19 @@ def process_sms_or_email_notification(
     )
     if document_download_count:
         # We changed personalisation which means we need to update the content
-        template.values = personalisation
+        template_with_content.values = personalisation
     key_type = api_key.key_type
     service_in_research_mode = service.research_mode
     resp = create_response_for_post_notification(
         notification_id=notification_id,
         client_reference=form.get('reference', None),
         template_id=template.id,
-        template_version=template._template['version'],
+        template_version=template.version,
         service_id=service.id,
         notification_type=notification_type,
         reply_to=reply_to_text,
         scheduled_for=form.get("scheduled_for", None),
-        template_with_content=template)
+        template_with_content=template_with_content)
 
     if str(service.id) in current_app.config.get('HIGH_VOLUME_SERVICE') and api_key.key_type == KEY_TYPE_NORMAL \
        and notification_type == EMAIL_TYPE:
@@ -229,7 +238,7 @@ def process_sms_or_email_notification(
     persist_notification(
         notification_id=notification_id,
         template_id=template.id,
-        template_version=template._template['version'],
+        template_version=template.version,
         recipient=form_send_to,
         service=service,
         personalisation=personalisation,
@@ -276,7 +285,7 @@ def save_email_to_queue(
     data = {
         "id": notification_id,
         "template_id": str(template.id),
-        "template_version": template._template['version'],
+        "template_version": template.version,
         "to": form['email_address'],
         "service_id": str(service_id),
         "personalisation": personalisation,
@@ -328,7 +337,7 @@ def process_document_uploads(personalisation_data, service, simulated=False):
 
 
 def process_letter_notification(
-    *, letter_data, api_key, template, template_with_content, reply_to_text, precompiled=False
+    *, letter_data, api_key, service, template, template_with_content, reply_to_text, precompiled=False
 ):
     if api_key.key_type == KEY_TYPE_TEAM:
         raise BadRequestError(message='Cannot send letters with a team api key', status_code=403)
@@ -339,6 +348,7 @@ def process_letter_notification(
     if precompiled:
         return process_precompiled_letter_notifications(letter_data=letter_data,
                                                         api_key=api_key,
+                                                        service=service,
                                                         template=template,
                                                         reply_to_text=reply_to_text)
 
@@ -360,6 +370,7 @@ def process_letter_notification(
     queue = QueueNames.CREATE_LETTERS_PDF if not test_key else QueueNames.RESEARCH_MODE
 
     notification = create_letter_notification(letter_data=letter_data,
+                                              service=service,
                                               template=template,
                                               api_key=api_key,
                                               status=status,
@@ -414,7 +425,7 @@ def validate_address(api_key, letter_data):
         )
 
 
-def process_precompiled_letter_notifications(*, letter_data, api_key, template, reply_to_text):
+def process_precompiled_letter_notifications(*, letter_data, api_key, service, template, reply_to_text):
     try:
         status = NOTIFICATION_PENDING_VIRUS_CHECK
         letter_content = base64.b64decode(letter_data['content'])
@@ -422,6 +433,7 @@ def process_precompiled_letter_notifications(*, letter_data, api_key, template,
         raise BadRequestError(message='Cannot decode letter content (invalid base64 encoding)', status_code=400)
 
     notification = create_letter_notification(letter_data=letter_data,
+                                              service=service,
                                               template=template,
                                               api_key=api_key,
                                               status=status,
@@ -460,7 +472,7 @@ def get_reply_to_text(notification_type, form, template):
         service_email_reply_to_id = form.get("email_reply_to_id", None)
         reply_to = check_service_email_reply_to_id(
             str(authenticated_service.id), service_email_reply_to_id, notification_type
-        ) or template.get_reply_to_text()
+        ) or template.reply_to_text
 
     elif notification_type == SMS_TYPE:
         service_sms_sender_id = form.get("sms_sender_id", None)
@@ -470,10 +482,10 @@ def get_reply_to_text(notification_type, form, template):
         if sms_sender_id:
             reply_to = try_validate_and_format_phone_number(sms_sender_id)
         else:
-            reply_to = template.get_reply_to_text()
+            reply_to = template.reply_to_text
 
     elif notification_type == LETTER_TYPE:
-        reply_to = template.get_reply_to_text()
+        reply_to = template.reply_to_text
 
     return reply_to