Add two-way messaging view

> Once an inbound message has been received, there should be a way to
> see the other messages in the system from the same service to the same
> number. Both in and outbound. Nice inbox/whatsapp stylee view or some
> such. This way the context of the reply is understood.
>
> Initially will only see the outbound template, not the actual message,
> but we’re going to change this for the rest (soon), so that you can
> always see the full message for all outbound.

tests/__init__.py

@@ -248,7 +248,9 @@ def notification_json(
             'template': {
                 'id': template['id'],
                 'name': template['name'],
-                'template_type': template['template_type']},
+                'template_type': template['template_type'],
+                'content': template['content'],
+            },
             'job': job_payload,
             'sent_at': sent_at,
             'status': status,