delete template cache when reply_to stuff is updated

sms sender, email reply to, letter contact blocks.

These are all cached within template, under `template.reply_to` - if the
template doesnt have a specific default, then that field stores the
service default. So when service default changes, we need to clear the
template cache so that it is updated to reflect that.

We already use this pattern for deleting the template cache for a bunch
of templates in `template_folder_api_client.move_to_folder`

tests/app/notify_client/test_service_api_client.py

@@ -413,6 +413,7 @@ def test_returns_value_from_cache(
 def test_deletes_service_cache(
     app_,
     mock_get_user,
+    mock_get_service_templates,
     mocker,
     client,
     method,
@@ -470,6 +471,7 @@ def test_deletes_caches_when_modifying_templates(
     method,
     extra_args,
     expected_cache_deletes,
+    mock_get_service_templates,
 ):
     mocker.patch('app.notify_client.current_user', id='1')
     mock_redis_delete = mocker.patch('app.extensions.RedisClient.delete')
@@ -477,7 +479,7 @@ def test_deletes_caches_when_modifying_templates(
 
     getattr(service_api_client, method)(*extra_args)
 
-    assert mock_redis_delete.call_args_list == list(map(call, expected_cache_deletes))
+    assert mock_redis_delete.call_args_list == [call(x) for x in expected_cache_deletes]
     assert len(mock_request.call_args_list) == 1
 
 
@@ -512,3 +514,41 @@ def test_client_updates_guest_list(mocker):
         url='/service/foo/guest-list',
         data=['a', 'b', 'c'],
     )
+
+
+def test_client_doesnt_delete_service_template_cache_when_none_exist(
+    app_,
+    mock_get_user,
+    mock_get_service_templates_when_no_templates_exist,
+    mocker
+):
+    mocker.patch('app.notify_client.current_user', id='1')
+    mocker.patch('notifications_python_client.base.BaseAPIClient.request')
+    mock_redis_delete = mocker.patch('app.extensions.RedisClient.delete')
+
+    service_api_client.update_reply_to_email_address(SERVICE_ONE_ID, uuid4(), 'foo@bar.com')
+
+    assert len(mock_redis_delete.call_args_list) == 1
+    assert mock_redis_delete.call_args_list[0] == call('service-{}'.format(SERVICE_ONE_ID))
+
+
+def test_client_deletes_service_template_cache_when_service_is_updated(
+    app_,
+    mock_get_user,
+    mock_get_service_templates,
+    mocker
+):
+    mocker.patch('app.notify_client.current_user', id='1')
+    mocker.patch('notifications_python_client.base.BaseAPIClient.request')
+    mock_redis_delete = mocker.patch('app.extensions.RedisClient.delete')
+
+    service_api_client.update_reply_to_email_address(SERVICE_ONE_ID, uuid4(), 'foo@bar.com')
+
+    assert len(mock_redis_delete.call_args_list) == 2
+    assert mock_redis_delete.call_args_list[1] == call('service-{}'.format(SERVICE_ONE_ID))
+
+    templates_to_delete = mock_redis_delete.call_args_list[0][0]
+    assert len(templates_to_delete) == 6
+    for template_key in templates_to_delete:
+        assert template_key.startswith('template-')
+        assert template_key.endswith('version-None')