Add log level and format configuration options for services

[zhuoyuan-liu]

Introduce configuration options for log level and format in services, allowing customization of logging behavior. This change enhances the flexibility of logging by enabling different log levels and formats through command-line flags and environment variables.

The change was made for admin and api. For tls, I would like to discuss a better naming convention:

• We need a configuration for server's logs
• We need another logger configuration for exports logs and results from osquery

Also, the code are highly duplicated and I would like to remove the duplication.

For documentation, do you know where should update these configuration options?

[javuto]

This is great, thank you for working on it!

If you are thinking having different flags for osctrl-tls, it would be good to follow the same convention for the three services.

What do you mean with We need another logger configuration for exports logs and results from osquery?

To update the documentation, clone the repository https://github.com/jmpsec/osctrl-docs, update the markdown in the content folder, and just run make to generate new HTML docs. Once the PR is merged, the documentation at https://osctrl.net will be automatically updated.

[javuto]

It is preferable to use Fatal() than to print the error and call exit, because closing writers and flushing buffers. See the implementation of Fatal() in zerolog:

// Fatal starts a new message with fatal level. The os.Exit(1) function
// is called by the Msg method, which terminates the program immediately.
//
// You must call Msg on the returned event in order to send the event.
func (l *Logger) Fatal() *Event {
	return l.newEvent(FatalLevel, func(msg string) {
		if closer, ok := l.w.(io.Closer); ok {
			// Close the writer to flush any buffered message. Otherwise the message
			// will be lost as os.Exit() terminates the program immediately.
			closer.Close()
		}
		os.Exit(1)
	})
}

[zhuoyuan-liu]

I think we cannot use Fatal() because the zerolog is not initialized.

[zhuoyuan-liu]

We will initialize the log after reading all the parameters.

[javuto]

I think we can use the same parameters in osctrl-tls for consistency, but there are some changes needed, thank you!

[zhuoyuan-liu]

@javuto I have updated the code according to your comments, could you please take another look.

[zhuoyuan-liu]

I think we cannot use Fatal() because the zerolog is not initialized.

[zhuoyuan-liu]

We will initialize the log after reading all the parameters.