Reload fixed_users config with API

[v1ack]

As for now, to reload config with fixed users, we need to restart entire service.
It's possible to make http handler to apiserver.config.basic.BasicConfig.reload function, to call it after config update, so new users will be able to auth without service restart

[v1ack]

@jkhenning hey, can also you comment that?

[jkhenning]

Hi @v1ack, I believe the issue is not so simple, since in some places the loaded config object might be cached (or parts of the configuration might be cached or stored in-memory), which might take quite some time to test and figure out.

In general, since we're using gunicorn to handle the worker processes for the apiserver component, and since gunicorn reloads these processes periodically anyway, a much simpler solution after updating the configuration files is to force the process reload in gunicorn using the kill -HUP command on the main gunicorn process inside the container - this can be automated by a script (i.e. execing into the container, finding the root gunicorn pid and issuing the command) - this would be the fastest solution and also the safest one (the processes will take a very short time to restart and gunicorn will wait with new HTTP requests for the workers to respond).