add CBC_PROXY_ENABLED config flag to control if tasks are triggered

previously we made some incorrect assumptions about set-up on staging
and prod - they currently don't have any cbc_proxy aws creds at all.

We shoudn't be attempting canaries or link tests when there's no AWS
infrastructure to connect to.

We also shouldn't bother writing a row into the database at all for the
broadcast_provider_message since we're not even attempting to send, and
we shouldn't get confused between messages that failed and messages we
never wanted to send at all.

tests/app/celery/test_broadcast_message_tasks.py

@@ -31,6 +31,18 @@ def test_send_broadcast_event_queues_up_for_active_providers(mocker, notify_api)
     ]
 
 
+def test_send_broadcast_event_does_nothing_if_cbc_proxy_disabled(mocker, notify_api):
+    mock_send_broadcast_provider_message = mocker.patch(
+        'app.celery.broadcast_message_tasks.send_broadcast_provider_message',
+    )
+
+    event_id = uuid.uuid4()
+    with set_config(notify_api, 'ENABLED_CBCS', ['ee', 'vodafone']), set_config(notify_api, 'CBC_PROXY_ENABLED', False):
+        send_broadcast_event(event_id)
+
+    assert mock_send_broadcast_provider_message.apply_async.called is False
+
+
 @freeze_time('2020-08-01 12:00')
 def test_send_broadcast_provider_message_sends_data_correctly(mocker, sample_service):
     template = create_template(sample_service, BROADCAST_TYPE)

tests/app/celery/test_scheduled_tasks.py

@@ -569,7 +569,7 @@ def test_send_canary_to_cbc_proxy_invokes_cbc_proxy_client(
 
     scheduled_tasks.send_canary_to_cbc_proxy()
 
-    mock_send_canary.assert_called
+    assert mock_send_canary.called is True
     # the 0th argument of the call to send_canary
     identifier = mock_send_canary.mock_calls[0][1][0]
 
@@ -579,6 +579,19 @@ def test_send_canary_to_cbc_proxy_invokes_cbc_proxy_client(
         pytest.fail(f"{identifier} is not a valid uuid")
 
 
+def test_send_canary_to_cbc_proxy_does_nothing_if_cbc_proxy_disabled(
+    mocker, notify_api
+):
+    mock_send_canary = mocker.patch(
+        'app.clients.cbc_proxy.CBCProxyCanary.send_canary',
+    )
+
+    with set_config(notify_api, 'CBC_PROXY_ENABLED', False):
+        scheduled_tasks.send_canary_to_cbc_proxy()
+
+    assert mock_send_canary.called is False
+
+
 def test_trigger_link_tests_calls_for_all_providers(
     mocker, notify_api
 ):
@@ -593,3 +606,16 @@ def test_trigger_link_tests_calls_for_all_providers(
         call(kwargs={'provider': 'ee'}, queue='notify-internal-tasks'),
         call(kwargs={'provider': 'vodafone'}, queue='notify-internal-tasks')
     ]
+
+
+def test_trigger_link_does_nothing_if_cbc_proxy_disabled(
+    mocker, notify_api
+):
+    mock_trigger_link_test = mocker.patch(
+        'app.celery.scheduled_tasks.trigger_link_test',
+    )
+
+    with set_config(notify_api, 'ENABLED_CBCS', ['ee', 'vodafone']), set_config(notify_api, 'CBC_PROXY_ENABLED', False):
+        trigger_link_tests()
+
+    assert mock_trigger_link_test.called is False

tests/app/clients/test_cbc_proxy.py

@@ -13,6 +13,7 @@ def cbc_proxy_client(client, mocker):
     current_app = mocker.Mock(config={
         'CBC_PROXY_AWS_ACCESS_KEY_ID': 'cbc-proxy-aws-access-key-id',
         'CBC_PROXY_AWS_SECRET_ACCESS_KEY': 'cbc-proxy-aws-secret-access-key',
+        'CBC_PROXY_ENABLED': True,
     })
     client.init_app(current_app)
     return client