vmauth cannot start with empty configuration.

[f41gh7]

Describe the bug

vmauth reports error if configuration file is empty. It makes impossible to start vmauth if it's needed to deploy it now and any configuration later.
Real world examples:

• helm charts
• victoria-metrics-operator

Current workaround for it:

• provide "fake" config section record with random local port. Which potentially a security risk and may confuse users.
• launch nginx server with vmauth and return static stab error.

It'd be great to accept empty configuration file and return UnAuthorized error for any request.

To Reproduce

Try to start vmauth with exists, but empty configuration file.

Version

Any version of vmauth.

Logs

No response

Screenshots

No response

Used command-line flags

No response

Additional information

No response

[hagen1778]

@f41gh7 would you mind describing scenario where this behavior will be essential?

I get it when vmalert or vmagent can be started without rules config or scrape config - they will just sit there, waiting to be utilized.

But with auth/reverse proxy it is different, from my perspective. Auth/reverse proxy supposed to be the only access point to resources, and without config it is not different to being just turned off. Even worse, it may confuse the user about wrong credentials when, in fact, there are no right credentials.