Use cached property from werkzeug.utils

This means we can have a method on the service model which hits the API
(or Redis) but can be called multiple times (within the context of a
request) without making multiple network requests.

It does this by storing the results of the method on the object’s
internal `__dict__` the first time the method is called.

app/notify_client/models.py

@@ -2,6 +2,7 @@ from itertools import chain
 
 from flask import request, session
 from flask_login import AnonymousUserMixin, UserMixin
+from werkzeug.utils import cached_property
 
 from app.utils import get_default_sms_sender
 
@@ -319,20 +320,20 @@ class Service():
     def has_permission(self, permission):
         return permission in self.permissions
 
-    @property
+    @cached_property
     def has_jobs(self):
         # Can’t import at top-level because app isn’t yet initialised
         from app import job_api_client
         return job_api_client.has_jobs(self.id)
 
-    @property
+    @cached_property
     def has_team_members(self):
         from app import user_api_client
         return user_api_client.get_count_of_users_with_permission(
             self.id, 'manage_service'
         ) > 1
 
-    @property
+    @cached_property
     def templates(self):
 
         from app import service_api_client
@@ -375,7 +376,7 @@ class Service():
     def has_sms_templates(self):
         return len(self.templates_by_type('sms')) > 0
 
-    @property
+    @cached_property
     def has_email_reply_to_address(self):
         from app import service_api_client
         return bool(service_api_client.get_reply_to_email_addresses(
@@ -390,7 +391,7 @@ class Service():
     def shouldnt_use_govuk_as_sms_sender(self):
         return self.organisation_type in {'local', 'nhs'}
 
-    @property
+    @cached_property
     def sms_sender_is_govuk(self):
         from app import service_api_client
         return get_default_sms_sender(

tests/app/main/views/test_templates.py

@@ -131,7 +131,7 @@ def test_should_show_page_for_choosing_a_template(
     for index, expected_template in enumerate(expected_templates):
         assert template_links[index].text.strip() == expected_template
 
-    mock_get_service_templates.assert_called_with(SERVICE_ONE_ID)
+    mock_get_service_templates.assert_called_once_with(SERVICE_ONE_ID)
 
 
 def test_should_not_show_template_nav_if_only_one_type_of_template(