add redact to notification with template schema.

So that when the admin gets notifications, the template they return
also has a "redact_personalisation" boolean attached to it. Note, it
won't do the redacting on the api - that'll be part of the admin.

Under the hood, this uses an association_proxy, which is essentially
black magic. But it proxies the `redact_personalisation` property of
`TemplateRedacted` onto the `Template` object, so that Marshmallow
can pick it up.

Note: NOT currently added to NotificationWithTemplateHistory

app/models.py

@@ -443,6 +443,8 @@ class Template(db.Model):
         default=NORMAL
     )
 
+    redact_personalisation = association_proxy('template_redacted', 'redact_personalisation')
+
     def get_link(self):
         # TODO: use "/v2/" route once available
         return url_for(

app/schemas.py

@@ -297,6 +297,11 @@ class BaseTemplateSchema(BaseSchema):
         strict = True
 
 
+class TemplateRedactedSchema(BaseSchema):
+    class Meta:
+        model = models.TemplateRedacted
+
+
 class TemplateSchema(BaseTemplateSchema):
 
     created_by = field_for(models.Template, 'created_by', required=True)
@@ -440,7 +445,7 @@ class NotificationWithTemplateSchema(BaseSchema):
 
     template = fields.Nested(
         TemplateSchema,
-        only=['id', 'version', 'name', 'template_type', 'content', 'subject'],
+        only=['id', 'version', 'name', 'template_type', 'content', 'subject', 'redact_personalisation'],
         dump_only=True
     )
     job = fields.Nested(JobSchema, only=["id", "original_file_name"], dump_only=True)