main_router decorator - not just for forms

[s-cork]

There's no reason why this has to be above a form. It could very easily be above a class loaded in a startup module.

This might make the whole - I have different top level forms - work much better than having to change your sidebars and nav bars.

I think this would take maybe 3 lines of code to work in the routing module.

Then the startup module might look like.

from anvil_extras import routing

@routing.main_router
class RouteManager:
    def on_navigation(self, url_hash, **nav_args):
        # some logic to replace the open form
        # some logic to adjust the look of the current top level form
        ...

route_manager = Manager()

The manager's job would be to make sure the top level form was correct given the hash. As well as to open the initial top level form.

And I guess to call any methods on the top level form that would formally have happened in an on_navigation call back method. (since the manager now intercepts this callback).