Serve an ASGI framework app given the config.
This allows for a programmatic way to serve an ASGI framework, it
can be used via,
It is assumed that the event-loop is configured before calling
this function, therefore configuration values that relate to loop
setup or process setup are ignored.
app – The ASGI application to serve.
config – A Hypercorn configuration object.
shutdown_trigger – This should return to trigger a graceful