Different page loaded after submission

When specifying the form in a different page and load it via twig, the url of the page gets loaded where the form is specified.
```
{% include "forms/form.html.twig" with { form: forms('unique-form-name') } %}
```

A current workaround is to set action to an empty string: `''`. I also want to note that the action defaults to the via constructor passed in `$page->route()`. Not only that this causes the issue, maybe `route` should be rather `url` here, but I will need to investigate some more.

Start by tracing the form included from forms/form.html.twig, including forms('unique-form-name'), the action value, and the constructor's $page->route(). Confirm how submission chooses the destination when the form is rendered on another page; done means submission remains on the page containing the form without requiring an empty action.

Written by the indexing model from the issue text.