Add TemplateHistory.get_link method

Notifications.serialize calls `Notifications.template.get_link`, so
we need TemplateHistory objects to generate their API URLs.

This generates a link to the `/v2/` version of the endpoint.

app/models.py

@@ -645,6 +645,14 @@ class TemplateHistory(db.Model):
                              nullable=False,
                              default=NORMAL)
 
+    def get_link(self):
+        return url_for(
+            "v2_template.get_template_by_id",
+            template_id=self.id,
+            version=self.version,
+            _external=True
+        )
+
     def _as_utils_template(self):
         return Template._as_utils_template(self)
 

tests/app/v2/notifications/test_get_notifications.py

@@ -335,7 +335,7 @@ def test_get_all_notifications_filter_by_template_type(client):
     assert json_response['notifications'][0]['status'] == "created"
     assert json_response['notifications'][0]['template'] == {
         'id': str(email_template.id),
-        'uri': email_template.get_link(),
+        'uri': notification.template.get_link(),
         'version': 1
     }
     assert json_response['notifications'][0]['email_address'] == "don.draper@scdp.biz"