feat: add SERVER_NAME to passthru config if specified in app config

[dhensen]

This does not work as expected:

@app.main_process_start
async def update_server_name(app, loop):
    some_url = some_reason()
    if some_url:
        app.update_config({"SERVER_NAME": some_url})

Problem

I would have expected my SERVER_NAME update to have propagated to workers, especially since doing this on main_process_start, but this is not the case. Because I have SANIC_SERVER_NAME env var set to some different value, all my workers still take that value, even though I just updated it with a new value.

Solution

With this PR, code above now works, and I can optionally change my SERVER_NAME at main_process_start and all my workers will have the correct SERVER_NAME.

[dhensen]

Converted to draft: when auto_reload=True this method does not update SERVER_NAME.
False alarm, I got fooled by my logs. Scrolled up too far, this scroll issue happened consistently 5 times when double checking. 😓

BTW: any idea why all those checks are failing? I see lint errors on files I did not touch.