Remove update_organisation_name model method

It’s weird to have a method just for updating one attribute. I think
the reason for doing this was to only invalidate the
`organisation-{}-name` cache when absolutely necessary, but:
- we don’t need a separate method to check whether it’s the name being
  updated
- it was easy to get around this by calling
  `OrganisationsClient.update_organisation` directly, leaving a stale
  value in the cache

app/notify_client/organisations_api_client.py

@@ -56,11 +56,10 @@ class OrganisationsClient(NotifyAdminAPIClient):
         if cached_service_ids:
             redis_client.delete(*map('service-{}'.format, cached_service_ids))
 
-        return api_response
+        if 'name' in kwargs:
+            redis_client.delete(f'organisation-{org_id}-name')
 
-    @cache.delete('organisation-{org_id}-name')
-    def update_organisation_name(self, org_id, name):
-        return self.update_organisation(org_id, name=name)
+        return api_response
 
     @cache.delete('service-{service_id}')
     @cache.delete('live-service-and-organisation-counts')

tests/app/notify_client/test_organisation_client.py

@@ -140,17 +140,34 @@ def test_deletes_domain_cache(
     assert len(mock_request.call_args_list) == 1
 
 
-def test_update_organisation_when_not_updating_org_type(mocker, fake_uuid):
+@pytest.mark.parametrize('post_data, expected_cache_delete_calls', (
+    ({'foo': 'bar'}, [
+        call('organisations'),
+        call('domains'),
+    ]),
+    ({'name': 'new name'}, [
+        call('organisation-6ce466d0-fd6a-11e5-82f5-e0accb9d11a6-name'),
+        call('organisations'),
+        call('domains'),
+    ]),
+))
+def test_update_organisation_when_not_updating_org_type(
+    mocker,
+    fake_uuid,
+    post_data,
+    expected_cache_delete_calls,
+):
+
     mock_redis_delete = mocker.patch('app.extensions.RedisClient.delete')
     mock_post = mocker.patch('app.notify_client.organisations_api_client.OrganisationsClient.post')
 
-    organisations_client.update_organisation(fake_uuid, foo='bar')
+    organisations_client.update_organisation(fake_uuid, **post_data)
 
     mock_post.assert_called_with(
         url='/organisations/{}'.format(fake_uuid),
-        data={'foo': 'bar'}
+        data=post_data
     )
-    assert mock_redis_delete.call_args_list == [call('organisations'), call('domains')]
+    assert mock_redis_delete.call_args_list == expected_cache_delete_calls
 
 
 def test_update_organisation_when_updating_org_type_and_org_has_services(mocker, fake_uuid):