The app should provide a minimal, non-intrusive UI (such as the "proactive chat" buttons we see on many websites), always visible over the host app's UI. When interacted with, this UI will summon the app in a new window.

This proposal uses both methods addEventListener and sendMessage to create intercommunication between the actual client application and the mock manager interface. By the use of this technique, it is possible to override the MSW handlers, change the mocked data at runtime, and keep the code of the Mock Manager and the client app separated into two different components trees.

To verify the behavior, do the following:

1. Reinstall the dependencies, because I've updated react;
2. Run the dev server with yarn run dev;
3. Open it up at http://localhost:1234/;
4. Submit the form;
5. See the message returned by the worker at the HTTP call interception (This is the original response message);
6. Click on "Open Mock Manager";
7. Enter some data in the JSON editor and submit it;
8. Return to the previous app (the one with the name-and-surname form) and try to submit the form again;
9. See the mocked data overridden by the data you've just entered in the Mock Manager form.

The override should be applied permanently by default, and continue to operate until the user disables it.

If the override is of the temporary type, it should run exactly once (see https://github.com/intesys/ymock/issues/4#issue-1250539039)

As different requests can be made to the same endpoint, based on the data provided during user interaction (i.e. different payloads, maybe with specific values, sent on a submit action), the app should provide the option to serve a specific mock variant in response to a specific request.