Allow callbacks to be removed

We’ve had a user who’s said:

> Seems configured callbacks cannot be removed once they’re set as the
> fields have a presence check. Is that intentional?

This means it’s not working as they expect. Rather than have to go and
change stuff in the database for them, let’s make it work as they’d
expect.

Only lets you clear the form if you remove both the token and the URL.

tests/app/main/views/test_api_integration.py

@@ -10,6 +10,8 @@ from tests import validate_route_permission
 from tests.conftest import (
     SERVICE_ONE_ID,
     fake_uuid,
+    mock_get_empty_service_callback_api,
+    mock_get_empty_service_inbound_api,
     mock_get_live_service,
     mock_get_notifications,
     mock_get_service,
@@ -478,7 +480,7 @@ def test_should_validate_whitelist_items(
     ('main.received_text_messages_callback'),
 ])
 @pytest.mark.parametrize('url, bearer_token, expected_errors', [
-    ("", "", "Can’t be empty Can’t be empty"),
+    ("https://example.com", "", "Can’t be empty"),
     ("http://not_https.com", "1234567890", "Must be a valid https URL"),
     ("https://test.com", "123456789", "Must be at least 10 characters"),
 ])
@@ -509,6 +511,71 @@ def test_callback_forms_validation(
     assert error_msgs == expected_errors
 
 
+@pytest.mark.parametrize('existing_values, callback_ids, delete_should_be_called', [
+    ((
+        mock_get_valid_service_callback_api,
+        mock_get_valid_service_inbound_api,
+    ), [fake_uuid()], True),
+    ((
+        mock_get_empty_service_callback_api,
+        mock_get_empty_service_inbound_api,
+    ), [], False),
+])
+@pytest.mark.parametrize('endpoint, expected_delete_url', [
+    (
+        'main.delivery_status_callback',
+        '/service/{}/delivery-receipt-api/{}',
+    ),
+    (
+        'main.received_text_messages_callback',
+        '/service/{}/inbound-api/{}',
+    ),
+])
+def test_callback_forms_can_be_cleared(
+    client_request,
+    service_one,
+    existing_values,
+    callback_ids,
+    delete_should_be_called,
+    endpoint,
+    expected_delete_url,
+    mocker,
+):
+
+    service_one['service_callback_api'] = callback_ids
+    service_one['inbound_api'] = callback_ids
+    mocked_delete = mocker.patch('app.service_api_client.delete')
+    for mock_get_callback in existing_values:
+        mock_get_callback(mocker)
+
+    service_one['permissions'] = ['inbound_sms']
+
+    page = client_request.post(
+        endpoint,
+        service_id=service_one['id'],
+        _data={
+            'url': '',
+            'bearer_token': '',
+        },
+        _expected_redirect=url_for(
+            'main.api_callbacks',
+            service_id=service_one['id'],
+            _external=True,
+        )
+    )
+
+    assert not page.select(".error-message")
+
+    if delete_should_be_called:
+        mocked_delete.assert_called_once_with(
+            expected_delete_url.format(
+                service_one['id'], callback_ids[0]
+            )
+        )
+    else:
+        assert mocked_delete.call_args_list == []
+
+
 @pytest.mark.parametrize('has_inbound_sms, expected_link', [
     (True, 'main.api_callbacks'),
     (False, 'main.delivery_status_callback'),

tests/conftest.py

@@ -2720,6 +2720,22 @@ def mock_get_valid_service_callback_api(mocker):
     return mocker.patch('app.service_api_client.get_service_callback_api', side_effect=_get)
 
 
+@pytest.fixture(scope='function')
+def mock_get_empty_service_inbound_api(mocker):
+    return mocker.patch(
+        'app.service_api_client.get_service_inbound_api',
+        side_effect=lambda service_id, callback_api_id: None,
+    )
+
+
+@pytest.fixture(scope='function')
+def mock_get_empty_service_callback_api(mocker):
+    return mocker.patch(
+        'app.service_api_client.get_service_callback_api',
+        side_effect=lambda service_id, callback_api_id: None,
+    )
+
+
 @pytest.fixture(scope='function')
 def mock_create_service_inbound_api(mocker):
     def _create_service_inbound_api(service_id, url, bearer_token, user_id):
@@ -2728,6 +2744,14 @@ def mock_create_service_inbound_api(mocker):
     return mocker.patch('app.service_api_client.create_service_inbound_api', side_effect=_create_service_inbound_api)
 
 
+@pytest.fixture(scope='function')
+def mock_delete_service_inbound_api(mocker):
+    return mocker.patch(
+        'app.service_api_client.delete_service_callback_api',
+        side_effect=lambda service_id: None
+    )
+
+
 @pytest.fixture(scope='function')
 def mock_update_service_inbound_api(mocker):
     def _update_service_inbound_api(service_id, url, bearer_token, user_id, inbound_api_id):
@@ -2744,6 +2768,14 @@ def mock_create_service_callback_api(mocker):
     return mocker.patch('app.service_api_client.create_service_callback_api', side_effect=_create_service_callback_api)
 
 
+@pytest.fixture(scope='function')
+def mock_delete_service_callback_api(mocker):
+    return mocker.patch(
+        'app.service_api_client.delete_service_callback_api',
+        side_effect=lambda service_id: None
+    )
+
+
 @pytest.fixture(scope='function')
 def mock_update_service_callback_api(mocker):
     def _update_service_callback_api(service_id, url, bearer_token, user_id, callback_api_id):